answer.code: In function ‘void dfs2(int, int)’:
answer.code:85:8: error: ‘sort’ is not a member of ‘std’
   85 |   std::sort(ae.begin(), ae.end());
      |        ^~~~
answer.code:86:8: error: ‘sort’ is not a member of ‘std’
   86 |   std::sort(ce.begin(), ce.end());
      |        ^~~~
answer.code: In function ‘int main()’:
answer.code:91:8: warning: ignoring return value of ‘int scanf(const char*, ...)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   91 |   scanf("%d%d", &n, &m);
      |   ~~~~~^~~~~~~~~~~~~~~~
answer.code:93:10: warning: ignoring return value of ‘int scanf(const char*, ...)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   93 |     scanf("%d%d", &from[i], &to[i]);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~