/in/foo.cc: In function 'void bfs(int)':
/in/foo.cc:34:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int i=0;i<g[u].size();++i) {
                      ~^~~~~~~~~~~~
/in/foo.cc: In function 'void dfs2(int)':
/in/foo.cc:51:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i=0;i<g2[u].size();++i) {
               ~^~~~~~~~~~~~~