#include "highway.h"
#include <bits/stdc++.h>
using namespace std;
using lint = long long;
const lint INF = 1e8;
const lint MAXN = 150005;
lint N, M, A, B;
vector<int> G[MAXN];
lint dist[MAXN];
int S, T;
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) || (v == o.v && u < o.u);
}
};
vector<edge> E;
void bfs(int n) {
queue<int> q;
int step = 0;
q.push(n);
for (; q.size(); step++) {
int sz = q.size();
while (sz--) {
int f = q.front();
q.pop();
if (dist[f] != INF) continue;
dist[f] = step;
for (auto &g : G[f]) {
if (dist[g] == INF) q.push(g);
}
}
}
}
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);
}
vector<int> guess(M, 0);
lint D = ask(guess) / A;
lint le, ri, ans, check;
/* find and edge e = uv, then construct tree rooted from u and from v */
le = 0, ri = M - 1;
while (le <= ri) {
lint mid = (le + ri) / 2;
guess.assign(M, 0);
for (int i = 0; i <= mid; i++) guess[i] = 1;
check = ask(guess);
if (check > D * A) {
ans = mid;
ri = mid - 1;
} else {
le = mid + 1;
}
}
int root = E[ans].u;
/* binary search from to find the opther pair */
for (int i = 0; i < N; i++) dist[i] = INF;
bfs(root);
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());
le = 0, ri = M - 1;
ans = (dist[E.back().u] > dist[E.back().v])? E.back().u : E.back().v;
while (le <= ri) {
guess.assign(M, 1); //how to find path when there are many paths?
lint mid = (le + ri) / 2; //we can just set all edges to heavy
for (int i = 0; i <= mid; i++) guess[E[i].id] = 0; //and binary search by setting 0...mid to light
check = ask(guess); //then the other edges become obsolete, and we can get the endpoint of the shortest path easily
if (check == D * A) {
ans = mid;
ri = mid - 1;
} else {
// ans = mid;
le = mid + 1;
}
}
S = E[ans].v;
/* found one pair, now find the other one */
for (int i = 0; i < N; i++) dist[i] = INF;
bfs(S);
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());
le = 0, ri = M - 1;
ans = (dist[E.back().u] > dist[E.back().v])? E.back().u : E.back().v;
while (le <= ri) { //then we can do the same thing to find T from root S, by the same logic
guess.assign(M, 1);
lint mid = (le + ri) / 2;
for (int i = 0; i <= mid; i++) guess[E[i].id] = 0;
check = ask(guess);
if (check == D * A) {
ans = mid;
ri = mid - 1;
} else {
// ans = mid;
le = mid + 1;
}
}
ans = E[ans].v;
T = ans;
/* found one pair, now find the other one */
// cout << S << " " << T << "\n";
answer(S, T);
}
/*
4 4 1 3 1 0
0 1
0 2
0 3
1 2
4 3 1 3 0 1
0 1
0 2
0 3
4 3 1 3 2 3
0 1
0 3
1 2
*/
