/in/foo.cc: In function 'void dfs(int)':
/in/foo.cc:15:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<G[dep].size();i++) dfs(G[dep][i]);
              ~^~~~~~~~~~~~~~
/in/foo.cc:16:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<G[dep].size();i++) {
              ~^~~~~~~~~~~~~~
/in/foo.cc: In function 'int find_root()':
/in/foo.cc:25:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^