#include "highway.h"
#include <bits/stdc++.h>
#define int long long
using namespace std;
struct edge{
int id, v;
};
int N, M, A, B;
vector<vector<edge> > graph;
void dfs(int u, int par, int id, int d, int dist, vector<int>& idlist, vector<int>& vlist){
if(d == dist){
idlist.push_back(id);
vlist.push_back(u);
}
for(edge e : graph[u]) if(e.v!=par){
dfs(e.v, u, e.id, d+1, dist, idlist, vlist);
}
}
int findT(int S, int par, int dist, int id){
vector<int> idlist, vlist;
dfs(S, par, id, 0, dist, idlist, vlist);
int L = 0, R = idlist.size();
while(L!=R-1){
int Mi = (L+R)/2;
vector<signed> w(M, 0);
for(int i = 0; i<Mi; i++){
w[idlist[i]]=1;
}
if(ask(w)==dist*A){
L = Mi;
}
else{
R = Mi;
}
}
return vlist[L];
}
void find_pair(signed _N, vector<signed> U, vector<signed> V, signed _A, signed _B) {
N = _N;
M = U.size();
A = _A;
B = _B;
graph.resize(N);
for(int i = 0; i<M; i++){
graph[U[i]].push_back({i, V[i]});
graph[V[i]].push_back({i, U[i]});
}
vector<signed> w(M, 0);
int dist = ask(w)/A;
answer(0, findT(0, 0, dist, -1));
}
