answer.code: In function ‘int DSU::merge(int, int)’:
answer.code:22:34: error: expected ‘;’ before ‘if’
   22 |                 if(!u) swap(u, v)
      |                                  ^
      |                                  ;
   23 |                 if(v) fa[v] = u, nxt[v] = head[u], head[u] = v;
      |                 ~~                
answer.code: In function ‘void CAT::mdfr(int, int, int, int)’:
answer.code:86:38: warning: structured bindings only available with ‘-std=c++17’ or ‘-std=gnu++17’
   86 |                                 auto [pl, x] = q1[id[u]].top();
      |                                      ^
answer.code:95:38: warning: structured bindings only available with ‘-std=c++17’ or ‘-std=gnu++17’
   95 |                                 auto [pr, x] = q2[id[u]].top();
      |                                      ^
answer.code: In function ‘void CAT::mdfl(int, int, int, int)’:
answer.code:113:38: warning: structured bindings only available with ‘-std=c++17’ or ‘-std=gnu++17’
  113 |                                 auto [pr, x] = q2[id[u]].top();
      |                                      ^
answer.code:122:38: warning: structured bindings only available with ‘-std=c++17’ or ‘-std=gnu++17’
  122 |                                 auto [pl, x] = q1[id[u]].top();
      |                                      ^