#include "highway.h"
#include <bits/stdc++.h>
#define fr first
#define sc second
#define mk make_pair
#define pb push_back
using namespace std;
const int QWE = 1e5 + 5;
int n, len, m, a, b, h[QWE];
vector < vector <pair <int, int> > > g;
vector <int> w, u1, u2;
vector <int> vec[QWE];
void dfs (int v, int level = 0, int p = -1)
{
h[v] = level;
for (auto to : g[v])
{
if (to.fr == p) continue;
vec[level + 1].pb(to.sc);
dfs(to.fr, level + 1, v);
}
}
int Find(int root)
{
dfs(root);
int l = -1, r = vec[len / a].size() - 1;
while (r - l > 1)
{
int md = (l + r) >> 1;
for (int i = 0; i < m; i++)
w[i] = 0;
for (int i = 0; i <= md; i++)
w[ vec[len / a][i] ] = 1;
if ( ask(w) != len )
r = md;
else
l = md;
}
if ( h[ u1[ vec[len / a][r] ] ] > h[ u2[ vec[len / a][r] ] ] )
return u1[ vec[len / a][r] ];
return u2[ vec[len / a][r] ];
}
void find_pair(int N, std::vector<int> U, std::vector<int> V, int A, int B)
{
u1 = U;
u2 = V;
a = A;
b = B;
n = N;
g.resize(n + 1);
m = U.size();
for (int j = 0; j < m; ++j)
{
w.pb(0);
g[ U[j] ].pb( mk( V[j], j) );
g[ V[j] ].pb( mk( U[j], j) );
}
len = ask(w);
answer( 0, Find(0) );
}
/**
4 3 1 3 0 3
0 1
0 2
0 3
**/
