foo.c: In function 'cal':
foo.c:31:19: error: expected expression before ')' token
   31 |         if (flag==)
      |                   ^
foo.c:33:34: error: 'i' undeclared (first use in this function)
   33 |                 for (int i=cnt-1;i>=0;i--)
      |                                  ^
foo.c:33:34: note: each undeclared identifier is reported only once for each function it appears in

[Hydro](https://hydro.ac)提供评测服务