/in/foo.cc: In function 'int main()':
/in/foo.cc:36:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for(int j=0;j<G[i].size();j++)
                ~^~~~~~~~~~~~
/in/foo.cc:45:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int j=0;j<G[k].size();j++)
                 ~^~~~~~~~~~~~
/in/foo.cc:62:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for(int j=0;j<G[i].size();j++)
                ~^~~~~~~~~~~~
/in/foo.cc:71:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int j=0;j<G[k].size();j++)
                 ~^~~~~~~~~~~~