#include "highway.h"
#include <bits/stdc++.h>
#ifndef EVAL
#include "grader.cpp"
#endif
using namespace std;
#define pb push_back
#define sz(x) (int)x.size()
#define ff first
#define ss second
const int NN = 1e5+5;
vector<pair<int, int>> edges[NN];
vector<int> tr;
int ans;
int dfs(int u, int p){
if(sz(edges[u]) == 1){
return u;
}
for(auto x:edges[u]){
if(x.ff == p) continue;
tr[x.ss] = 1;
int ver = ask(tr);
if(ver == ans){
tr[x.ss] = 0;
continue;
}
else{
tr[x.ss] = 0;
return dfs(x.ff, u);
}
} return 0;
}
void find_pair(int N, vector<int> U, vector<int> V, int A, int B) {
for(int i=0;i<sz(V);i++){
edges[V[i]].pb({U[i], i});
edges[U[i]].pb({V[i], i});
}
tr.resize(sz(V), 0);
ans = ask(tr);
int res = dfs(0, -1);
//cout<<0<<" "<<res<<"\n";
answer(0, res);
}
/*
7 6 1 2 0 5
0 1
0 4
1 2
1 3
4 5
4 6
*/
