#include <bits/stdc++.h>
#include <highway.h>
using namespace std;
#define ll long long
#define pb push_back
#define mp make_pair
#define F first
#define S second
const int N = 150005;
pair <int, int> par[N];
vector < pair <int, int> > adj[N];
int flat[N], timer;
void dfs(int v, int p) {
flat[timer++] = v;
for(auto &u: adj[v]) {
if(u.F == p) continue;
par[u.F] = {v, u.S};
dfs(u.F, v);
}
return;
}
void find_pair(int n, vector <int> u, vector <int> v, int a, int b) {
int i, m, l, r, mid, s, t;
vector <int> w(n - 1);
ll max_cost;
m = u.size();
for(i = 0; i < m; i++) {
adj[u[i]].pb({v[i], i});
adj[v[i]].pb({u[i], i});
}
dfs(0, -1);
w.resize(m, 1);
max_cost = ask(w);
w.resize(m, 0);
l = 1; r = n - 1;
while(l + 1 < r) {
mid = (l + r) / 2;
for(i = l; i <= mid; i++)
w[par[flat[i]].S] = 1;
if(ask(w) < max_cost) l = mid;
else {
r = mid;
for(i = l; i <= mid; i++)
w[par[flat[i]].S] = 0;
}
}
s = flat[l + 1];
w.resize(m, 0);
timer = 0;
memset(flat, 0, sizeof(flat));
memset(par, 0, sizeof(par));
dfs(s, -1);
l = 1; r = n - 1;
while(l + 1 < r) {
mid = (l + r) / 2;
for(i = l; i <= mid; i++)
w[par[flat[i]].S] = 1;
if(ask(w) < max_cost) l = mid;
else {
r = mid;
for(i = l; i <= mid; i++)
w[par[flat[i]].S] = 0;
}
}
t = flat[l + 1];
assert(s >= 0 && s < n && t >= 0 && t < n);
answer(s, t);
return;
}
