#include<bits/stdc++.h>
using namespace std;
#define intt long long
#define pb push_back
#define forr(i , x , y) for(int i = x; i <= y;i++)
#define fore(i , n) for(int i = 0 ; i < n;i++)
#define forn(i ,x , y) for(int i = x ; i >= y;i--)
long long ask(const vector<int> &w);
void answer(int s, int t);
const int MAXN = 90001;
intt a , b;
vector<pair<int ,int>> adj[MAXN];
vector<int> zeros , ones;
int dfs(int x , int p , intt val , int dep)
{
if(dep == (val/b))
return x;
vector<pair<int ,int>> v;
for(auto [u , i] : adj[x])
{
if(u == p)
continue;
v.pb({u , i});
}
int sz = (int)v.size();
if((int)v.size() == 1)
{
return dfs(v[0].first , x , val , dep + 1);
}
int l = 0 , r = sz;
vector<int> asked = ones;
while(l + 1 < r)
{
int mid = (l + r)/2;
asked = ones;
forr(i , 0 , mid - 1)
asked[v[i].second] = 0;
if(ask(asked) == val)
l = mid;
else
r = mid;
}
int nxt = v[l].first;
return dfs(nxt , x , val , dep + 1);
}
int findT(int S)
{
intt val = ask(ones);
intt dist = val/b;
return dfs(S , -1 , val ,0);
}
void find_pair(int N, vector<int> U, vector<int> V, int A, int B)
{
a = A , b = B;
int m = (int)U.size();
zeros.assign(m , 0);
ones.assign(m , 1);
fore(i , m)
{
adj[U[i]].pb({V[i] , i});
adj[V[i]].pb({U[i] , i});
}
answer(0 ,findT(0));
}
