/in/foo.cc: In function 'int main()':
/in/foo.cc:14:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     while (i < s.size())
            ~~^~~~~~~~~~
/in/foo.cc:17:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         while (j < s.size() && s[j]!=' ')
                ~~^~~~~~~~~~
/in/foo.cc:27:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         if (j < s.size())
             ~~^~~~~~~~~~