#include "highway.h"
#include <bits/stdc++.h>
#define pb push_back
#define ppb pop_back
#define F first
#define S second
#define ll long long
#define elif else if
using namespace std;
const int NN=1e5;
vector<int> w;
vector<pair<int,int>> adj[NN];
int n,m,sz[NN],dep[NN],mxdep[NN],p[NN];
bool vis[NN];
ll dis;
bool cmp(pair<int,int> x,pair<int,int> y){
return sz[x.F]<sz[y.F];
}
void getsz(int x,int par){
sz[x]=1;
for (auto u:adj[x]){
if (vis[u.F] || u.F==par) continue;
getsz(u.F,x);
sz[x]+=sz[u.F];
}return;
}
int get_centroid(int x,int cursz,int par){
for (auto u:adj[x]){
if (vis[u.F] || u.F==par) continue;
if (sz[u.F]*2>cursz) return get_centroid(u.F,cursz,x);
}return x;
}
void dfs(int x,int par){
for (auto u:adj[x]){
if (vis[u.F] || u.F==par) continue;
w[u.S]=1;
dfs(u.F,x);
}return;
}
int centroid_decomposition(int x){
getsz(x,-1);
if (sz[x]<=2) return x;
int centroid=get_centroid(x,sz[x],-1);
getsz(centroid,-1);
//cout<<centroid<<endl;
sort(adj[centroid].begin(),adj[centroid].end(),cmp);
int sum=0;
for (int i=0;i<m;i++) w[i]=0;
for (auto u:adj[centroid]){
if (vis[u.F]) continue;
if (2*(sum+sz[u.F])>sz[centroid]) break;
sum+=sz[u.F];
//cout<<u.F<<' ';
w[u.S]=1;
dfs(u.F,centroid);
}//cout<<endl;
ll h=ask(w);
//cout<<h<<endl;
//for (auto u:w) cout<<u;cout<<endl;
for (auto u:adj[centroid]){
if (vis[u.F]) continue;
if (w[u.S] && dis==h){
vis[u.F]=1;
//cout<<u.F<<' ';
}
if (!w[u.S] && dis<h){
vis[u.F]=1;
//cout<<u.F<<' ';
}
}
//cout<<endl<<endl;
return centroid_decomposition(centroid);
}
void getdep(int x,int par){
mxdep[x]=dep[x];
for (auto u:adj[x]){
if (u.F==par) continue;
p[u.F]=u.S;
dep[u.F]=dep[x]+1;
getdep(u.F,x);
mxdep[x]=max(mxdep[x],mxdep[u.F]);
}return;
}
void dfss(int x,int par){
for (auto u:adj[x]){
if (u.F==par || mxdep[u.F]<dis || dep[u.F]>dis) continue;
w[u.S]=1;
dfss(u.F,x);
}return;
}
void find_pair(int N, std::vector<int> U, std::vector<int> V, int A, int B){
n=N;
m=U.size();
for (int i=0;i<m;i++){
adj[U[i]].pb({V[i],i});
adj[V[i]].pb({U[i],i});
}
w.resize(m);
dis=ask(w);
int s=centroid_decomposition(0),h;
//cout<<s<<endl;
for (auto u:adj[s]) if (!vis[u.F]) h=u.F;
if (dis==A){
answer(s,h);
return;
}
for (int i=0;i<n;i++) vis[i]=0;
for (int i=0;i<m;i++) w[i]=0;
getdep(s,-1);
dis/=A;
dfss(s,-1);
ll f=ask(w);
//cout<<s<<' '<<h<<endl;
if (f!=dis*(ll)B) swap(s,h),dep[s]=0,getdep(s,-1);
vector<int> v;
for (int i=0;i<n;i++){
if (dep[i]==dis) v.pb(i);
}
while (v.size()>1){
int mid=v.size()/2;
for (int i=0;i<m;i++) w[i]=0;
for (int i=0;i<mid;i++) w[p[v[i]]]=1;
f=ask(w);
if (f>dis*(ll)A){
while (v.size()>mid) v.ppb();
}
else{
reverse(v.begin(),v.end());
for (int i=0;i<mid;i++) v.ppb();
}
}
//cout<<s<<endl;
answer(s,v[0]);
return;
}
