/in/foo.cc: In function 'int main()':
/in/foo.cc:10:8: warning: unused variable 'sum' [-Wunused-variable]
  int t,sum;
        ^~~
/in/foo.cc: In function 'int yh(int, int)':
/in/foo.cc:27:44: warning: no return statement in function returning non-void [-Wreturn-type]
    if(tg[i][j]==0){sum++;}}}cout<<sum<<" ";};
                                            ^