foo.c: In function 'main':
foo.c:9:17: error: 'a' undeclared (first use in this function)
    9 |                 a=10000/365;//有几年   27年
      |                 ^
foo.c:9:17: note: each undeclared identifier is reported only once for each function it appears in
foo.c:14:33: error: 'b' undeclared (first use in this function)
   14 |                                 b=10000-365*a+1;
      |                                 ^
foo.c:5:22: warning: unused variable 'D' [-Wunused-variable]
    5 |     int YY,MM,DD,Y,M,D;
      |                      ^
foo.c:5:20: warning: unused variable 'M' [-Wunused-variable]
    5 |     int YY,MM,DD,Y,M,D;
      |                    ^
foo.c:5:18: warning: unused variable 'Y' [-Wunused-variable]
    5 |     int YY,MM,DD,Y,M,D;
      |                  ^

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