/in/foo.cc: In function 'int main()':
/in/foo.cc:11:7: warning: unused variable 's' [-Wunused-variable]
  char s[100];
       ^
/in/foo.cc:14:10: warning: unused variable 'i0' [-Wunused-variable]
  int i,j,i0,j0,k;
          ^~
/in/foo.cc:14:13: warning: unused variable 'j0' [-Wunused-variable]
  int i,j,i0,j0,k;
             ^~
/in/foo.cc:45:6: warning: unused variable 'b' [-Wunused-variable]
  int b[400]={0},dq=0,a=m*n;
      ^