/in/foo.cc: In function 'int dfs(int, int)':
/in/foo.cc:11:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0;i<G[v].size();i++)  
                 ~^~~~~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:46:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             for(int j=0;j<G[i].size();j++)  
                         ~^~~~~~~~~~~~