#include <bits/stdc++.h>
#include "highway.h"
using namespace std;
using ll = long long;
using pii = pair<int, int>;
vector<vector<pii>> adj;
vector<int> endp;
vector<int> edge;
int t;
vector<int> query;
ll w;
void dfs(int n, int p) {
for (auto x : adj[n]) {
if (x.second == p) continue;
endp[t] = x.second;
edge[x.first] = t++;
dfs(x.second, n);
}
}
int first(int M) {
int l = 0, r = M-1;
int ans = 0;
while (l <= r) {
int m = (l+r)/2;
for (int i=0; i<M; i++) {
query[i] = (i <= m);
}
ll w2 = ask(query);
if (w2 != w) {
r=m-1;
}
else {
l = m+1;
ans = m+1;
}
}
return ans;
}
int last(int M) {
int l=0, r = t-1;
int ans=-1;
while (l <= r) {
int m = (l+r+1)/2;
for (int i=0; i<M; i++) {
query[i] = (edge[i] >= m);
}
ll w2 = ask(query);
if (w2 != w) {
l = m+1;
ans = m;
}
else {
r = m-1;
}
}
return ans;
}
void find_pair(int n, vector<int> U, vector<int> V, int A, int B) {
int m = U.size();
query.assign(m, 0);
w = ask(query);
adj.resize(n);
for (int i=0; i<m; i++) {
int a = U[i];
int b = V[i];
adj[a].push_back({i, b});
adj[b].push_back({i, a});
}
edge.resize(m);
endp.resize(m);
t=0;
dfs(0, -1);
int e = first(m);
int v = U[e];
int u = V[e];
vector<int> ans(2);
//cout << e << endl;
for (int i=0; i<2; i++) {
t = 0;
edge.assign(m, -1);
dfs(v, u);
int le = last(m);
//cout << le << endl;
ans[i] = (le==-1 ? v : endp[le]);
//cout << ans[i] << endl;
swap(v, u);
}
answer(ans[0], ans[1]);
}
