/in/foo.cc: In function 'int main(int, char**)':
/in/foo.cc:13:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i = 0;i<s.size();i++)
                ~^~~~~~~~~
/in/foo.cc:25:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0;i < qs.size();i++){
                 ~~^~~~~~~~~~~
/in/foo.cc:29:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int j = i+1;j<qs.size();j++)
                   ~^~~~~~~~~~