CF - Ostap & Tree

Solution described by editorial is terrible, but we can do better! This runs in $\mathcal{O}(NK)$ time. (proof?)

1#include <bits/stdc++.h>
2using namespace std;
3 
4using ll = long long;
5using ld = long double;
6using db = double; 
7using str = string; // yay python!
8
9using pi = pair<int,int>;
10using pl = pair<ll,ll>;