/in/foo.cc: In function 'int main()':
/in/foo.cc:21:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i = 0; i < winner.size(); i += 2)
                   ~~^~~~~~~~~~~~~~~
/in/foo.cc:23:10: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    if (i < winner.size() - 1)
        ~~^~~~~~~~~~~~~~~~~~~
/in/foo.cc:35:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i = 0; i < winner2.size(); i++)
                   ~~^~~~~~~~~~~~~~~~