#include "highway.h"
#include <bits/stdc++.h>
using namespace std;
//macros
typedef long long ll;
typedef pair<int, int> ii;
typedef tuple<int, int, int> iii;
typedef vector<int> vi;
typedef vector<ii> vii;
typedef vector<iii> viii;
typedef vector<ll> vll;
#define REP(a,b,c) for(int a=int(b); a<int(c); a++)
#define RE(a,c) REP(a,0,c)
#define RE1(a,c) REP(a,1,c+1)
#define REI(a,b,c) REP(a,b,c+1)
#define REV(a,b,c) for(int a=int(c-1); a>=int(b); a--)
#define pb push_back
#define fi first
#define se second
#define sz size()
//===================//
// begin program //
//===================//
const int MX = 5e5;
int n, m, a, b, e;
vi w, u, v;
vii adj[MX];
ll dist;
vi onPath, visited;
int getS(vii& binU, vii& binV) {
// binaray search for s
int lb=0, ub=binU.sz-1;
while(lb != ub) {
int mid=(lb+ub+1)/2;
RE(i,m) w[i] = 1;
for(ii p:binV) w[p.se] = 0;
RE(i,mid) w[binU[i].se] = 0;
if(ask(w) == dist) ub = mid-1;
else lb = mid;
}
return binU[lb].fi;
}
void find_pair(int N, vi U, vi V, int A, int B) {
n=N; a=A; b=B; u=U; v=V;
m = u.sz;
RE(i,m) {
adj[u[i]].pb({v[i], i});
adj[v[i]].pb({u[i], i});
}
w.assign(m, 0);
dist = ask(w);
// get edge e on path s - t
int lb=0, ub=m-1;
while(lb != ub) {
int mid=(lb+ub)/2;
RE(i,m) w[i] = 1;
RE(i,mid+1) w[i] = 0;
if(ask(w) == dist) ub = mid;
else lb = mid+1;
}
e = lb;
// bfs
visited.assign(n, 0);
vii binU, binV;
queue<pair<int, bool>> q;
q.push({u[e],1}); visited[u[e]] = 1; binU.pb({u[e], e});
q.push({v[e],0}); visited[v[e]] = 1; binV.pb({v[e], e});
while(!q.empty()) {
auto u = q.front(); q.pop();
for(ii v : adj[u.fi]) {
if(visited[v.fi]) continue;
visited[v.fi] = 1;
q.push({v.fi, u.se});
if(u.se) binU.pb(v);
else binV.pb(v);
}
}
int s = getS(binU, binV);
int t = getS(binV, binU);
answer(s, t);
}
