/in/foo.cc: In function 'void dfs(int)':
/in/foo.cc:10:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   10 |         for(int i=0;i<g[x].size();i++)
      |                     ~^~~~~~~~~~~~
/in/foo.cc:18:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   18 |         for(int i=0;i<a.size();i++)//ai是打电话时间
      |                     ~^~~~~~~~~