/in/foo.cc: In function 'int main()':
/in/foo.cc:9:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i < s.length()+1; i++)
                  ~~^~~~~~~~~~~~~~
/in/foo.cc:12:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int j = 1; j < s.length()-i+1; j++)
                   ~~^~~~~~~~~~~~~~~~
/in/foo.cc:16:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for (int k = 0; k < ss.length() + 1; k++)
                    ~~^~~~~~~~~~~~~~~~~