#include <map>
#include <unordered_map>
#include <unordered_set>
#include <set>
#include <vector>
#include <numeric>
#include <algorithm>
#include <iostream>
#include <string>
#include <cstring>
#include <sstream>
#include <functional>
#include <queue>
#include <deque>
#include <stack>
#include <cassert>
#include <iomanip>
#include <cmath>
#include <bitset>
using namespace std;
#include "highway.h"
using int64 = long long;
// cache
map<pair<int, int>, int> eidx;
int eget(int u, int v) {
if (u > v) swap(u, v);
return eidx[{u, v}];
}
void eset(int u, int v, int idx) {
if (u > v) swap(u, v);
eidx[{u, v}] = idx;
}
//
vector<vector<int>> adj;
vector<int> tree_idx;
vector<int> comp;
vector<int> dist;
vector<int> par;
void find_pair(int N, std::vector<int> U, std::vector<int> V, int A, int B) {
int M = U.size();
int S = -1;
int T = -1;
// Step 0. Find min dist, 1 query
vector<int> w(M);
int64 D = ask(w) / A;
// Step 1. Find edge on min - path, 18 queries worst-case (!)
int l = 0, r = M - 1, sol = -1;
while (l <= r) {
int m = (l + r) >> 1;
w.assign(M, 0);
for (int i = 0; i <= m; i++)
w[i] = 1;
int64 cur = ask(w);
if (cur > D * A) {
sol = m;
r = m - 1;
} else {
l = m + 1;
}
}
assert(sol != -1);
cerr << "Critical edge: " << U[sol] << " -> " << V[sol] << "\n";
cerr << "D: " << D << "\n";
adj.assign(N, vector<int>{});
for (int i = 0; i < M; i++) {
adj[ U[i] ].push_back( V[i] );
adj[ V[i] ].push_back( U[i] );
eset(U[i], V[i], i);
}
int x = U[sol];
int y = V[sol];
queue<int> Q;
Q.push(x);
Q.push(y);
dist.assign(N, -1);
par.assign(N, -1);
comp.assign(N, -1);
comp[x] = 0;
comp[y] = 1;
dist[x] = 0;
dist[y] = 0;
tree_idx.push_back(eget(x, y));
for (; !Q.empty(); ) {
auto el = Q.front();
Q.pop();
for (auto v : adj[el]) {
if (dist[v] == -1) {
dist[v] = dist[el] + 1;
comp[v] = comp[el];
par[v] = el;
tree_idx.push_back(eget(el, v));
Q.push(v);
}
}
}
assert(tree_idx.size() == N - 1);
// TODO: Remove
w.assign(M, 1);
for (auto e : tree_idx) {
w[e] = 0;
}
assert(ask(w) == D * A);
//
w.assign(M, 1);
for (int i = 0; i < N; i++) {
if (par[i] != -1 && comp[i] == 0) {
w[eget(i, par[i])] = 0;
}
}
int64 depth = ask(w);
bool ok = false;
for (int64 i = 0; i < N; i++) {
if (i * A + (D - i) * B == depth) {
depth = i;
ok = true;
break;
}
}
assert(ok);
auto solve_half_tree = [&] (int x, int y, int cc, int depth, int & R) {
R = -1;
cerr << "solve_half_tree, start: " << x << " par: " << y << " " << cc << "\n";
cerr << "depth: " << depth << "\n";
if (!depth) {
R = x;
} else {
vector<int> cand;
for (int i = 0; i < N; i++) {
if (par[i] != -1 && dist[i] == depth && comp[i] == cc) {
cand.push_back(i);
}
}
assert(cand.size());
function<int(int, int)> rec = [&] (int l, int r) {
if (l == r) {
return cand[l];
}
int m = (l + r) >> 1;
vector<int> w(M, 1);
for (auto e : tree_idx)
w[e] = 0;
for (int i = l; i <= m; i++) {
w[eget(cand[i], par[cand[i]])] = 1;
}
bool ok = ask(w) > D * A;
if (ok) {
return rec(l, m);
} else {
return rec(m + 1, r);
}
};
R = rec(0, cand.size() - 1);
};
};
solve_half_tree(U[sol], V[sol], 0, depth, S);
solve_half_tree(V[sol], U[sol], 1, D - 1 - depth, T);
cerr << S << " " << T << "\n";
auto debug = [&](int _S, int _T) {
cerr << dist[_S] << " " << comp[_S] << "\n";
cerr << dist[_T] << " " << comp[_T] << "\n";
};
debug(44782, 77604);
//debug(RS, RT);
assert(S != T);
answer(S, T);
}
