#include "highway.h"
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
template<typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<typename T>
using ordered_multiset = tree<T, null_type, less_equal<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<typename T>
using min_heap = priority_queue<T, vector<T>, greater<T>>;
template<typename T>
using max_heap = priority_queue<T, vector<T>, less<T>>;
using int64 = long long;
using ld = long double;
constexpr int kInf = 1e9 + 10;
constexpr int64 kInf64 = 1e15 + 10;
constexpr int kMod = 1e9 + 7;
int find_hidden_node(const vector<vector<pair<int, int>>> &g, const int s, const int par, const int64 all_a, const vector<int> &template_w, const int a, const int b) {
vector<int> w = template_w;
function<void(int, int)> dfs1 = [&](const int x, const int p) {
for (const auto &[y, i] : g[x]) {
if (y == p) continue;
w[i] = 1;
dfs1(y, x);
}
};
dfs1(s, par);
const int64 this_b = ask(w);
const int depth = (this_b - all_a) / (b - a);
if (depth == 0) {
return s;
}
vector<pair<int, int>> candidates;
function<void(int, int, int, int)> dfs2 = [&](const int x, const int p, const int i, const int d) {
if (d == depth) {
candidates.emplace_back(x, i);
return;
}
for (const auto &[y, idx] : g[x]) {
if (y == p) continue;
dfs2(y, x, idx, d + 1);
}
};
dfs2(s, par, -1, 0);
int lo = 0, hi = candidates.size() - 1;
while (lo < hi) {
const int mid = (lo + hi) / 2;
for (int i = 0; i < candidates.size(); i++) {
w[candidates[i].second] = (i <= mid);
}
if (ask(w) < this_b) {
lo = mid + 1;
} else {
hi = mid;
}
}
return candidates[lo].first;
}
void find_pair(const int n, const vector<int> U, const vector<int> V, const int a, const int b) {
const int m = U.size();
vector<int> w(m);
const int64 all_a = ask(w);
int lo = 0, hi = m - 1;
while (lo < hi) {
const int mid = (lo + hi) / 2;
for (int i = 0; i < m; i++) {
w[i] = (i <= mid);
}
if (ask(w) > all_a) {
hi = mid;
} else {
lo = mid + 1;
}
}
assert(lo == hi);
vector<vector<pair<int, int>>> g(n);
for (int i = 0; i < m; i++) {
g[U[i]].emplace_back(V[i], i);
g[V[i]].emplace_back(U[i], i);
}
auto bfs = [&g](const int s) {
vector<int> dist(g.size(), kInf);
dist[s] = 0;
queue<int> q;
q.push(s);
while (not q.empty()) {
const int x = q.front();
for (const auto &[y, _] : g[x]) {
if (dist[y] < kInf) continue;
q.push(y);
dist[y] = dist[x] + 1;
}
q.pop();
}
return dist;
};
auto bfs_tree = [&](const int s, vector<int> near) -> vector<vector<pair<int, int>>> {
queue<int> q;
q.push(s);
vector<vector<pair<int, int>>> tree(n);
near[s] = 0;
while (not q.empty()) {
const int x = q.front();
for (const auto &[y, i] : g[x]) {
if (near[y] == 0) continue;
q.push(y);
tree[x].emplace_back(y, i);
near[y] = 0;
}
q.pop();
}
return tree;
};
const int x = U[lo], y = V[lo];
const vector<int> distx = bfs(x), disty = bfs(y);
vector<int> nearx(n), neary(n);
for (int i = 0; i < n; i++) {
nearx[i] = (distx[i] < disty[i]);
neary[i] = (disty[i] < distx[i]);
}
const auto tx = bfs_tree(x, nearx);
const auto ty = bfs_tree(y, neary);
vector<int> template_w(m, 1);
template_w[lo] = 0;
for (int u = 0; u < n; u++) {
for (const auto &[_, i] : tx[u]) {
template_w[i] = 0;
}
for (const auto &[_, i] : ty[u]) {
template_w[i] = 0;
}
}
assert(ask(template_w) == all_a);
answer(find_hidden_node(tx, x, y, all_a, template_w, a, b),
find_hidden_node(ty, y, x, all_a, template_w, a, b));
}
