#include<bits/stdc++.h>
#define pb push_back
#define ii pair<int,int>
#define all(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
#define modulo 1000000007
#define mod 998244353
using namespace std;
#include "highway.h"
vector<int>adj[200000];
vector<int> d;
vector<int> D(200000, 0);
map<ii, int> edge;
vector<int> ptr;
void dfs(int x, int pre, int dep){
for(auto y : adj[x]){
if(y == pre) continue;
d[edge[{x, y}]] = dep;
D[y] = D[x] + 1;
dfs(y, x, dep + 1);
}
}
void find_pair(int N, std::vector<int> U, std::vector<int> V, int A, int B) {
int M = U.size();
int mn = ask(vector<int>(M, 0));
for(int i = 0; i < M; i++){
edge[{U[i], V[i]}] = i;
edge[{V[i], U[i]}] = i;
ptr.pb(i);
adj[U[i]].pb(V[i]);
adj[V[i]].pb(U[i]);
d.pb(0);
}
auto lower = [&](int x){
D[x] = 0;
dfs(x, -1, 0);
sort(all(ptr), [&](int x, int y){return d[x] > d[y];});
int l = 0, r = M - 1;
int ret = M - 1;
while(l <= r){
int m = (l + r) / 2;
vector<int> Q(M, 0);
for(int i = 0; i <= m; i++) Q[ptr[i]] = 1;
if(ask(Q) != mn){
ret = m;
r = m - 1;
}
else l = m + 1;
}
return ptr[ret];
};
int b = 0, e = 0;
b = lower(0);
int bb = U[b];
if(D[V[b]] > D[U[b]]) bb = V[b];
e = lower(bb);
int ee = U[e];
if(D[V[e]] > D[U[e]]) ee = V[e];
if(bb > ee) swap(bb, ee);
answer(bb, ee);
}
