#include "highway.h"
#include <bits/stdc++.h>
using namespace std;
using lint = long long;
const lint MAXN = 150005;
lint N, M, A, B;
vector<int> G[MAXN];
lint dist[MAXN];
struct edge {
int u, v, id;
edge(int uu, int vv, int idd): u(uu), v(vv), id(idd) { }
bool operator < (const edge &o) {
return dist[v] < dist[o.v] || (dist[v] == dist[o.v] && v < o.v);
}
};
vector<edge> E;
void dfs(int n, int p, int d) {
dist[n] = d;
for (auto &i : G[n]) if (i != p) {
dfs(i, n, d + 1);
}
}
void find_pair(int _N, vector<int> U, vector<int> V, int _A, int _B) {
N = _N, A = _A, B = _B, M = U.size();
for (int i = 0; i < M; i++) {
G[U[i]].emplace_back(V[i]);
G[V[i]].emplace_back(U[i]);
E.emplace_back(U[i], V[i], i);
}
dfs(0, -1, 0);
for (int i = 0; i < M; i++) {
if (dist[E[i].u] > dist[E[i].v]) swap(E[i].u, E[i].v);
}
sort(E.begin(), E.end());
lint le = 0, ri = M - 1;
lint ans = (dist[E.back().u] > dist[E.back().v])? E.back().u : E.back().v;
vector<int> guess(M, 0);
lint D = ask(guess) / A;
while (le <= ri) {
guess.assign(M, 0);
lint mid = (le + ri) / 2;
for (int i = 0; i <= mid; i++) guess[E[i].id] = 1;
lint check = ask(guess);
// cout << le << " " << ri << " " << check << "\n";
if (check == D * B) {
ans = mid;
ri = mid - 1;
} else {
// ans = mid;
le = mid + 1;
}
}
// cout << ans << "\n";
ans = (dist[E[ans].u] == D)? E[ans].u : E[ans].v;
answer(0, ans);
}
/*
4 4 1 3 1 3
0 1
0 2
0 3
1 2
4 3 1 3 0 2
0 1
0 2
0 3
4 3 1 3 0 1
0 1
0 3
1 2
*/
