/in/foo.cc: In function 'int main()':
/in/foo.cc:38:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int j=0; j<g[u].size(); j++)
                       ~^~~~~~~~~~~~
/in/foo.cc:53:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int i=0; i<revg[u].size(); i++)
                       ~^~~~~~~~~~~~~~~