foo.cc: In function 'int main()':
foo.cc:21:15: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  int m,n;scanf("%d%d",&m,&n);
          ~~~~~^~~~~~~~~~~~~~
foo.cc:27:9: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%d",&a[i][j]);
    ~~~~~^~~~~~~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务