#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;
vector<int> nodes;
vector<pair<int ,int>> nds;
intt val;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
void dfs(int x , int p , intt dep)
{
if(dep == (val/b))
{
nodes.pb(x);
return;
}
for(auto [u , i] : adj[x])
{
if(u == p)
continue;
dfs(u , x ,dep + 1 );
}
}
void dfs1(int x , int p , int dep)
{
nds.pb({dep , x});
for(auto u : adj[x])
{
if(u.first == p)
continue;
dfs1(u.first , x , dep + 1);
}
}
int findT(int S)
{
dfs(S , -1 , 0);
int l = 0 , r = (int)nodes.size();
vector<int> asked = ones;
while(l + 1 < r)
{
int mid = (l + r)/2;
asked = ones;
forr(j , 0 , mid - 1) {
for(auto [u , i] : adj[nodes[j]])
asked[i] = 0;
}
if(ask(asked) == val)
l = mid;
else
r = mid;
}
return nodes[l];
}
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 , N)adj[i].clear();
val = ask(ones);
fore(i , m)
{
adj[U[i]].pb({V[i] , i});
adj[V[i]].pb({U[i] , i});
}
dfs1(0 , -1 , 0);
sort(nds.rbegin() , nds.rend());
int l = 0 , r = (int)nds.size();
vector<int> asked = ones;
while(l + 1 < r)
{
int mid = (l + r)/2;
asked = ones;
forr(j , 0 , mid - 1) {
for(auto i : adj[nds[j].second])asked[i.second] = 0;
}
if(ask(asked) == val)
l = mid;
else
r = mid;
}
int S = nds[l].second;
answer(S , findT(S));
}
