#include "highway.h"
#include <bits/stdc++.h>
using namespace std;
#define int long long
#define pii pair<int,int>
#define mp make_pair
#define pb push_back
#define fi first
#define se second
int n, m, k, a, b;
vector<vector<pii> > adj;
int calc(int start){
vector<pii> ord;
vector<int> dj(n, -1);
queue<int> q;
dj[start]=0;
q.push(start);
while (q.size()){
int node=q.front();
q.pop();
for (auto num:adj[node])if (dj[num.fi]==-1)dj[num.fi]=dj[node]+1, q.push(num.fi), ord.pb(mp(num.fi, num.se));
}
int low=-1, high=ord.size()-1;
while (low+1<high){
int mid=(low+high)/2;
vector<signed> temp(m, 1);
for (auto a:ord)temp[a.se]=0;
for (int i=mid; i<ord.size(); ++i)temp[ord[i].se]=1;
if (k==ask(temp))high=mid;
else low=mid;
}
return ord[low].fi;
}
void find_pair(signed N, vector<signed> u, vector<signed> v, signed A, signed B){
n=N, m=u.size(), a=A, b=B;
adj.clear();
adj.resize(n);
vector<pii> ord;
vector<signed> temp(m, 0);
k=ask(temp);
for (int i=0; i<m; ++i){
adj[u[i]].pb(mp(v[i], i));
adj[v[i]].pb(mp(u[i], i));
}
int low=0, high=m;
while (low+1<high){
int mid=(low+high)/2;
vector<signed> temp(m, 0);
for (int i=0; i<mid; ++i)temp[i]=1;
if (ask(temp)==k)low=mid;
else high=mid;
}
int s=calc(u[low]), t=calc(s);
answer(s, t);
}
