#include "highway.h"
#include <bits/stdc++.h>
using namespace std;
typedef pair<int, int> pii;
typedef long long ll;
const int maxn = 1e5 + 100;
int n;
vector<pii> g[maxn];
int p[maxn];
int f[maxn];
ll dist;
int calc(vector<int> s){
int v = -1;
for(int l = 0, r = s.size()-1; l <= r;){
int mid = (l + r) >> 1;
vector<int> q(n-1, 0);
for(int i = 0; i <= mid; i++){
q[f[s[i]]] = 1;
} if(ask(q) == dist) l = mid + 1;
else r = mid - 1, v = s[mid];
} return v;
}
void find_pair(int N, std::vector<int> U, std::vector<int> V, int A, int B) {
n = N;
dist = ask(vector<int>(N-1, 0));
for(int i = 0; i < n - 1; i++){
int a = U[i], b = V[i];
g[a].push_back({b, i});
g[b].push_back({a, i});
}
vector<int> s;
queue<int> q;
q.push(0);
while(q.size()){
int v = q.front();
q.pop();
for(auto [to, i]: g[v]){
if(to != p[v]){
p[to] = v;
f[to] = i;
q.push(to);
s.push_back(to);
}
}
} reverse(s.begin(), s.end());
int a = calc(s);
vector<int> ns;
int i = a;
for(int v: s){
if(v == i){
i = p[i];
continue;
} ns.push_back(v);
} int b = calc(ns);
if(b == -1){
ns.clear();
for(int i = a; i; i = p[i]){
ns.push_back(i);
} reverse(ns.begin(), ns.end());
b = p[calc(ns)];
} answer(a, b);
}
