#include "highway.h"
#include "bits/stdc++.h"
using namespace std;
using ll = long long;
#define sz(a) (int)a.size()
void dfs(int u, int par, vector<vector<int>>& adj, vector<int>& p, vector<int>& depth) {
p[u] = par;
for(int v: adj[u]) {
if(v == par) continue;
depth[v] = depth[u] + 1;
dfs(v, u, adj, p, depth);
}
}
map<vector<int>, ll> have;
ll query(vector<int> c) {
if(!have.count(c)) have[c] = ask(c);
return have[c];
}
int find(int start, int n, vector<int>& u, vector<int>& v) {
map<pair<int, int>, int> idx;
vector<vector<int>> adj(n);
vector<int> p(n, 0), depth(n, 0);
int m = u.size();
for(int i = 0; i < m; ++i) {
adj[u[i]].push_back(v[i]);
adj[v[i]].push_back(u[i]);
idx[{u[i], v[i]}] = idx[{v[i], u[i]}] = i;
}
dfs(start, -1, adj, p, depth);
int l = 1, r = n, dd = -1;
vector<int> c(m, 1);
ll init = query(c);
while(l <= r) {
int mid = (l + r) >> 1;
for(int j = 0; j < n; ++j) {
if(j == start) continue;
if(depth[j] >= mid) {
c[idx[{j, p[j]}]] = 0;
}
}
if(query(c) < init) {
dd = mid;
l = mid + 1;
} else r = mid - 1;
c.assign(m, 1);
}
vector<int> nodes;
for(int i = 0; i < n; ++i) {
if(i == start) continue;
if(depth[i] == dd) nodes.push_back(i);
}
assert(sz(nodes) > 0);
l = 0, r = sz(nodes) - 1;
int pp = -1;
while(l <= r) {
int mid = (l + r) >> 1;
for(int i = 0; i <= mid; ++i) {
assert(p[nodes[i]] != -1);
c[idx[{nodes[i], p[nodes[i]]}]] = 0;
}
if(query(c) < init) {
pp = mid;
r = mid - 1;
} else l = mid + 1;
c.assign(m, 1);
}
assert(pp != -1);
return nodes[pp];
}
void find_pair(int n, vector<int> u, vector<int> v, int a, int b) {
int s = find(0, n, u, v);
int t = find(s, n, u, v);
answer(t, s);
}
