foo.cc: In function 'int main()':
foo.cc:86:7: warning: unused variable 'j' [-Wunused-variable]
   86 | int i,j,a,b;char cc;
      |       ^
foo.cc:89:6: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   89 | scanf("%d%d",&n,&m);
      | ~~~~~^~~~~~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务