/in/foo.cc: In function 'void dfs(int, int, int)':
/in/foo.cc:12:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<G[u].size();i++){
              ~^~~~~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:19:24: error: expected primary-expression before 'return'
  if(n==6)cout<<3<<endl,return 0;
                        ^~~~~~