/in/foo.cc: In function 'int main()':
/in/foo.cc:16:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int j = 1; j < word.length(); j++)
                   ~~^~~~~~~~~~~~~~~
/in/foo.cc:36:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i < doc.length(); i++)
                  ~~^~~~~~~~~~~~~~
/in/foo.cc:43:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int j = 1; j < word.length(); j++)
                     ~~^~~~~~~~~~~~~~~