/in/foo.cc: In function 'void dfs1(int)':
/in/foo.cc:28:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(R int i=0;i<G[u].size();++i){
                ~^~~~~~~~~~~~
/in/foo.cc: In function 'void dfs2(int)':
/in/foo.cc:38:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(R int i=0;i<G[u].size();++i){
                ~^~~~~~~~~~~~