/in/foo.cc: In function 'int main()':
/in/foo.cc:29:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0;i<s.size();i++)
                 ~^~~~~~~~~
/in/foo.cc:41:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0;i<s.size();i++)
                 ~^~~~~~~~~