#include "highway.h"
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<pair<int, int>> vpi;
#define INF 1000000000
#define F first
#define S second
#define PB push_back
#define MP make_pair
#define rep(i,a,b) for (int i = a; i < b; i++)
typedef struct node {
int vertex, edge, dist;
node() {};
node(int a, int b, int c) : vertex(a), edge(b), dist(c) {};
} node;
vpi adj[90000];
vi tree_adj[90000];
vi edge_dist[90000];
bool seen[90000];
int subtree_sizes[90000];
int depth[90000];
void make_spanning_tree(int cur) {
seen[cur] = 1;
for (auto p : adj[cur]) {
int edge = p.F;
if (!seen[edge]) {
make_spanning_tree(edge);
tree_adj[cur].PB(edge);
tree_adj[edge].PB(cur);
}
}
}
void find_sizes(int cur) {
seen[cur] = 1;
subtree_sizes[cur] = 1;
for (auto edge : tree_adj[cur]) {
if (!seen[edge]) {
find_sizes(edge);
subtree_sizes[cur] += subtree_sizes[edge];
}
}
}
int find_centroid(int N) {
find_sizes(0);
int centroid = 0, largest_subtree, nxt = 0;
do {
centroid = nxt;
largest_subtree = 0;
for (auto edge : adj[centroid]) {
if (subtree_sizes[edge.F] > largest_subtree) {
largest_subtree = subtree_sizes[N];
nxt = edge.F;
}
}
} while(largest_subtree >= N/2+5 && N - subtree_sizes[centroid] >= N/2+5);
return centroid;
}
void find_pair(int N, vi U, vi V, int A, int B) {
int S, T, M = V.size();
ll dist;
vi w(M, 0); //query edge list
rep(i,0,M) {
adj[U[i]].emplace_back(V[i], i);
adj[V[i]].emplace_back(U[i], i);
}
make_spanning_tree(0);
memset(seen, 0, sizeof(seen));
queue<pii> bfs;
bfs.push(MP(find_centroid(N), 1));
int tree_height = 0;
while (!bfs.empty()) {
pii cur = bfs.front(); bfs.pop(); //vertex, distance
depth[cur.F] = cur.S;
tree_height = max(tree_height, cur.S);
seen[cur.F] = 1;
for (auto edge : adj[cur.F]) {
edge_dist[cur.S].PB(edge.S);
if (!seen[edge.F]) bfs.push(MP(edge.F, cur.S+1));
}
}
assert(A > 0);
dist = ask(w)/A;
int low = 1, high = tree_height;
while (low < high) {
int mid = (low + high)/2;
for (int i = tree_height-1; i >= mid; i--) {
for (auto edge : edge_dist[i]) w[edge] = 1;
}
ll res = ask(w);
if (res > dist*A) low = mid+1;
else high = mid;
memset(&w[0], 0, sizeof(w[0])*M);
}
int lower_point = low-1; //depth of lower point
low = 0, high = edge_dist[lower_point].size();
while (low < high) {
int mid = (low + high)/2;
for (int i = 0; i <= mid; i++) w[edge_dist[lower_point][i]] = 1;
ll res = ask(w);
if (res > dist*A) high = mid;
else low = mid+1;
memset(&w[0], 0, sizeof(w[0])*M);
}
S = min(U[edge_dist[lower_point][low]], V[edge_dist[lower_point][low]]);
if (depth[U[edge_dist[lower_point][low]]] > depth[V[edge_dist[lower_point][low]]]) S = U[edge_dist[lower_point][low]];
else S = V[edge_dist[lower_point][low]];
queue<node> bfs2;
bfs2.push(node(S, 0, 0));
memset(seen, 0, sizeof(seen));
while (!bfs2.empty()) {
auto cur = bfs2.front(); bfs2.pop();
seen[cur.vertex] = 1;
if (dist == cur.dist) {
w[cur.edge] = 1;
ll res = ask(w);
if (res > dist*A) {
T = cur.vertex;
break;
}
w[cur.edge] = 0;
}
for (auto edge : adj[cur.vertex]) {
if (!seen[edge.F]) {
bfs2.push(node(edge.F, edge.S, cur.dist+1));
}
}
}
answer(S, T);
}
