/in/foo.cc: In function 'int main()':
/in/foo.cc:10:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int i = 0; i < s.size(); i++) {
                          ^
/in/foo.cc:15:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int i = 0; i < s.size(); i++) cout << s[i];
                          ^