#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
#define vv vector
typedef pair<int, int> pii;
const int NN = 1e5+5;
vv<pii> edges[NN];
vector<int> tr;
int ans;
int dfs(int u, int p){
if(sz(edges[u]) == 1) return u;
vv<pii> tt;
for(auto x:edges[u]) if(x.ff != p) tt.pb(x);
int l = 0, r = sz(tt)-1;
while(l+1 < r){
//cout<<l<<" "<<r<<" "<<u<<"\n";
int m = (l + r)>>1;
for(int i=m;i<sz(tt);i++) tr[tt[i].ss] = 1;
int res = ask(tr);
if(res == ans){
for(int i=m;i<sz(tt);i++) tr[tt[i].ss] = 0;
r = m-1;
}else{
for(int i=m;i<sz(tt);i++) tr[tt[i].ss] = 0;
//if(l == m) break;
l = m;
}
}
int m = r;
for(int i=m;i<sz(tt);i++) tr[tt[i].ss] = 1;
int res = ask(tr);
if(res != ans){
for(int i=m;i<sz(tt);i++) tr[tt[i].ss] = 0;
l = m;
}
//cout<<tt[l].ff<<"\n";
return dfs(tt[l].ff, u);
}
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);
answer(0, dfs(0, -1));
}
/*
7 6 1 2 0 5
0 1
0 4
1 2
1 3
4 5
4 6
*/
