#include "highway.h"
#include <bits/stdc++.h>
using namespace std;
#define int long long
int val,dep,s=0,e;
vector<int32_t> vec;
vector<pair<int,int>> pos;
vector<vector<pair<int,int>>> edges;
void run(int now,int par,int d){
for(int i=0;i<edges[now].size();i++){
if(edges[now][i].first==par){
continue;
}else if(d==dep-1){
pos.push_back(edges[now][i]);
}else{
run(edges[now][i].first,now,d+1);
}
}
}
int search(int l,int r){
if(l==r){
return l;
}
int m=(l+r)/2;
fill(vec.begin(),vec.end(),0);
for(int i=0;i<=m;i++){
vec[pos[i].second]=1;
}
if(ask(vec)!=val){
return search(l,m);
}
return search(m+1,r);
}
void find_pair(int32_t N, std::vector<int32_t> U, std::vector<int32_t> V, int32_t A, int32_t B) {
edges.resize(N);
for(int i=0;i<U.size();i++){
edges[U[i]].push_back({V[i],i});
edges[V[i]].push_back({U[i],i});
}
vec.resize(U.size(),0);
val=ask(vec);
dep=val/A;
run(0,-1,0);
// cout << val << ' ' << dep << '\n';
answer(0,pos[search(0,pos.size()-1)].first);
}
