表达式21: "D" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, left parenthesis, "x" , "y" , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis less than or equal to 2Dffffffffffffffffffx,y≤2
21
表达式22: "D" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, left parenthesis, "x" , "y" , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis less than or equal to 2Dfffffffffffffffffffx,y≤2
22
表达式23: "D" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, left parenthesis, "x" , "y" , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis less than or equal to 2Dffffffffffffffffffffx,y≤2
23
表达式24: "D" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, left parenthesis, "x" , "y" , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis less than or equal to 2Dfffffffffffffffffffx,y≤2
24
表达式25: "D" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, left parenthesis, "x" , "y" , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis less than or equal to 2Dffffffffffffffffffffx,y≤2
25
表达式26: "D" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, left parenthesis, "x" , "y" , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis less than or equal to 2Dfffffffffffffffffffffx,y≤2
26
表达式27: "D" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, left parenthesis, "x" , "y" , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis less than or equal to 2Dffffffffffffffffffffffx,y≤2
27
表达式28: "D" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, left parenthesis, "x" , "y" , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis less than or equal to 2Dfffffffffffffffffffffffx,y≤2
28
表达式29: "D" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, left parenthesis, "x" , "y" , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis less than or equal to 2Dffffffffffffffffffffffffx,y≤2
29
表达式30: "D" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, left parenthesis, "x" , "y" , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis less than or equal to 2Dfffffffffffffffffffffffffx,y≤2
30
表达式31: "D" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, left parenthesis, "x" , "y" , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis less than or equal to 2Dffffffffffffffffffffffffffx,y≤2
31
表达式32: "D" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, left parenthesis, "x" , "y" , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis less than or equal to 2Dfffffffffffffffffffffffffffx,y≤2
32
表达式33: "D" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, left parenthesis, "x" , "y" , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis less than or equal to 2Dffffffffffffffffffffffffffffx,y≤2
33
表达式34: "D" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, left parenthesis, "x" , "y" , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis less than or equal to 2Dfffffffffffffffffffffffffffffx,y≤2
34
表达式35: "D" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, left parenthesis, "x" , "y" , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis less than or equal to 2Dffffffffffffffffffffffffffffffx,y≤2
35
表达式36: "D" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, left parenthesis, "x" , "y" , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis less than or equal to 2Dfffffffffffffffffffffffffffffffx,y≤2
36
表达式37: "D" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, left parenthesis, "x" , "y" , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis less than or equal to 2Dffffffffffffffffffffffffffffffffx,y≤2
37
表达式38: "D" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, "f" left parenthesis, left parenthesis, "x" , "y" , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis , right parenthesis less than or equal to 2Dfffffffffffffffffffffffffffffffffx,y≤2
