/in/foo.cc: In function 'int main()':
/in/foo.cc:35:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < s.length(); i++)
                     ~~^~~~~~~~~~~~
/in/foo.cc:151:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < ans1.size(); i++)
                     ~~^~~~~~~~~~~~~
/in/foo.cc:153:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int j = 0; j < ans2.size(); j++)
                         ~~^~~~~~~~~~~~~