/in/foo.cc: In function 'int main()':
/in/foo.cc:7:15: warning: 'm' is used uninitialized in this function [-Wuninitialized]
  for(int i=0;i<m;i++)
              ~^~
/in/foo.cc:17:16: warning: 'n' may be used uninitialized in this function [-Wmaybe-uninitialized]
   for(int j=0;j<n;j++)
               ~^~