foo.cc: In function 'void dfs(int, int, int)':
foo.cc:46:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<a[now].size();i++){
              ~^~~~~~~~~~~~~~
foo.cc:41:6: warning: unused variable 'maxdepth' [-Wunused-variable]
  int maxdepth=depth;
      ^~~~~~~~
foo.cc: In function 'void solve()':
foo.cc:55:13: warning: variable 'root' set but not used [-Wunused-but-set-variable]
  int yuan=n,root=-1;
             ^~~~

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