/in/foo.cc: In member function 'void Cow::tarjan(int)':
/in/foo.cc:38:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i=0; i<graph[k].size(); i++){
                ~^~~~~~~~~~~~~~~~
/in/foo.cc: In member function 'void Cow::dfs(int)':
/in/foo.cc:64:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i=0; i<graph2[k].size(); i++){
                ~^~~~~~~~~~~~~~~~~