/in/foo.cc: In function 'void dfs(int, int)':
/in/foo.cc:18:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i=0;i<g[v].size();i++) {
                  ~^~~~~~~~~~~~
/in/foo.cc:24:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i=0;i<g[v].size();i++) {
               ~^~~~~~~~~~~~
/in/foo.cc:33:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i=0;i<g[v].size();i++) {
                  ~^~~~~~~~~~~~