foo.c: In function 'main':
foo.c:19:31: error: redefinition of 'num'
   19 |         int b = 0, c = n - 1, num = 0;
      |                               ^~~
foo.c:8:18: note: previous definition of 'num' with type 'int'
    8 |         int i, j,num=0;
      |                  ^~~

[Hydro](https://hydro.ac)提供评测服务