/in/foo.cc: In function 'int main()':
/in/foo.cc:108:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for(int i=0;i<ha[x].size();i++){
                ~^~~~~~~~~~~~~
/in/foo.cc:88:13: warning: 'rt' may be used uninitialized in this function [-Wmaybe-uninitialized]
  dfs2(rt,rt);
             ^