/in/foo.cc: In function 'int main()':
/in/foo.cc:63:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for (i = 0;i < s.size() - 1;i++)
               ~~^~~~~~~~~~~~~~
/in/foo.cc:81:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
       for (j = i + 1;j < s.size() - 1;j++)
                      ~~^~~~~~~~~~~~~~