/in/foo.cc: In function 'void dfs(int)':
/in/foo.cc:43:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<Q[u].size();i++)
              ~^~~~~~~~~~~~
/in/foo.cc:48:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<G[u].size();i++)
              ~^~~~~~~~~~~~
/in/foo.cc:53:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<a[u].size();i++)
              ~^~~~~~~~~~~~