#include "highway.h"
#include<bits/stdc++.h>
#define ll long long
#define ull unsigned ll
#define f first
#define s second
#define pii pair<int,int>
#define pll pair<ll,ll>
#define pb push_back
#define epb emplace_back
using namespace std;
const int NMAX = 1e6 + 1;
vector <vector <int> > g(NMAX);
int d[NMAX];
vector <int> p(NMAX, -1);
int n;
ll a, b;
void bfs(int s){
d[s] = 0;
for(int i = 0; i < n; i++){
p[i] = -1;
d[i] = 1e9;
}
queue <int> q;
q.push(s);
int cnt = 1;
p[s] = 0;
d[s] = 0;
while(!q.empty()){
int v = q.front();
q.pop();
for(int to : g[v]){
if(p[to] != -1) continue;
d[to] = cnt++;
p[to] = v;
q.push(to);
}
}
}
void find_pair(int N, std::vector<int> U, std::vector<int> V, int A, int B) {
vector <int> bb;
n = N;
int m = U.size();
for(int i = 0; i < m; i++){
bb.pb(0);
g[U[i]].pb(V[i]);
g[V[i]].pb(U[i]);
}
a = A;
b = B;
const vector <int> vv = bb;
ll mn = ask(bb);
bfs(0);
int l = 0, r = n;
while(l + 1 < r){
int mid = (l + r) / 2;
vector <int> vec;
for(int i = 0; i < m; i++){
if(d[U[i]] <= mid && d[V[i]] <= mid)vec.pb(0);
else vec.pb(1);
}
const vector <int> vv = vec;
ll x = ask(vv);
if(x == mn) r = mid;
else l = mid;
}
for(int i = 0; i < n; i++) if(d[i] == r) {
r = i;
break;
}
bfs(r);
int l1 = 0, r1 = n;
while(l1 + 1 < r1){
int mid = (l1 + r1) / 2;
vector <int> vec;
for(int i = 0; i < m; i++){
if(d[U[i]] <= mid && d[V[i]] <= mid) vec.pb(0);
else vec.pb(1);
}
const vector <int> vv = vec;
ll x = ask(vv);
if(x == mn) r1 = mid;
else l1 = mid;
}
for(int i = 0; i < n; i++) if(d[i] == r1){
r1 = i;
break;
}
answer(r, r1);
}
