foo.cc: In function 'void dfs(int)':
foo.cc:42:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i=0; i<a[x].size(); ++i)
                ~^~~~~~~~~~~~
foo.cc: In function 'void DP()':
foo.cc:77:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i=0; i<c.size(); ++i)
                ~^~~~~~~~~
foo.cc: In function 'void init()':
foo.cc:23:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&N);
  ~~~~~^~~~~~~~~

正在同步测试数据，请稍后
自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。