// ItnoE
#include<bits/stdc++.h>
#include "highway.h"
using namespace std;
typedef long long ll;
const int N = 100005, MXN = N * 2;
int n, m, ts, X, Y, H[N], Mark[N], V[MXN], U[MXN];
ll ndist, dist;
vector < int > Q, Adj[N];
inline void BFS(int root)
{
memset(H, -1, sizeof(H));
H[root] = 0;
queue < int > qu;
qu.push(root);
while (qu.size())
{
int v = qu.front();
qu.pop();
for (int id : Adj[v])
{
int u = V[id] ^ U[id] ^ v;
if (H[u] == -1)
H[u] = H[v] + 1, qu.push(u);
}
}
}
inline int GetHeight()
{
int Mxh = 0;
for (int i = 0; i < n; i ++)
Mxh = max(Mxh, H[i]);
int le = 1, ri = Mxh + 1, md;
while (ri - le > 1)
{
md = (le + ri) >> 1;
for (int i = 0; i < m; i ++)
Q[i] = 0;
for (int i = 0; i < n; i ++)
if (H[i] >= md)
for (int id : Adj[i])
{
int u = V[id] ^ U[id] ^ i;
if (H[u] < H[i])
Q[id] = 1;
}
ll dd = ask(Q);
if (dd == dist)
ri = md;
else
le = md;
}
return (le);
}
inline int FindS(int h)
{
ts ++;
vector < int > vec;
for (int i = 0; i < n; i ++)
if (H[i] == h && (ts == 1 || Mark[i] == 1))
vec.push_back(i);
int le = 0, ri = (int)vec.size(), md;
while (ri - le > 1)
{
md = (le + ri) >> 1;
for (int i = 0; i < m; i ++)
Q[i] = 0;
for (int i = le; i < md; i ++)
for (int id : Adj[vec[i]])
{
int u = V[id] ^ U[id] ^ vec[i];
if (H[u] < H[vec[i]])
Q[id] = 1;
}
ll dd = ask(Q);
if (dd == dist)
le = md;
else
ri = md;
}
return (vec[le]);
}
void find_pair(int _n, vector < int > _V, vector < int > _U, int _X, int _Y)
{
n = _n;
m = (int)_V.size();
X = _X; Y = _Y;
for (int i = 0; i < m; i ++)
{
V[i] = _V[i]; U[i] = _U[i];
Adj[V[i]].push_back(i);
Adj[U[i]].push_back(i);
}
Q = vector < int > (m, 0);
dist = ask(Q);
ndist = dist / X;
int le = 0, ri = n, md;
while (ri - le > 1)
{
md = (le + ri) >> 1;
for (int i = le; i < md; i ++)
for (int id : Adj[i])
Q[id] = 1;
ll dd = ask(Q);
for (int i = le; i < md; i ++)
for (int id : Adj[i])
Q[id] = 0;
if (dist == dd)
le = md;
else
{
for (int i = le; i < md; i ++)
for (int id : Adj[i])
Q[id] = 0;
ri = md;
}
}
int root = le;
{
for (int id : Adj[root])
Q[id] = 1;
ll dd = ask(Q);
if (dd == dist)
assert(0);
}
BFS(root);
int hs = GetHeight();
int ht = ndist - hs;
for (int i = 0; i < n; i ++)
if (H[i] == ht)
Mark[i] = 1;
int s = FindS(hs);
BFS(s);
int t = FindS(ndist);
answer(s, t);
}
