/in/foo.cc: In function 'int main()':
/in/foo.cc:108:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i = 1; i <= m; i++){
                 ~~^~~~
/in/foo.cc:115:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i = 1; i <= n; i++)
                 ~~^~~~
/in/foo.cc:116:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int j = 0; j <= k; j++)
                  ~~^~~~