#include "highway.h"
#include<bits/stdc++.h>
#define K 1<<17
using namespace std;
int pos[2][K],par[2][K],pari[2][K],dis[2][K];
vector<pair<int,int>>adj[K];
void bfs(int n,int i){
queue<int>q;
int CC=0;
memset(dis[i],-1,sizeof *pos);
q.push(n);
dis[i][n]=0;
par[i][n]=-1;
while(q.size()){
int x=q.front(),d=dis[i][x];
q.pop(); pos[i][x]=++CC;
for(auto [j,k]:adj[x]) if(dis[i][j]<0)
par[i][j]=x,pari[i][j]=k,
dis[i][j]=d+1,q.push(j);
}
}
int indd,dep2=-1,actD;
int whicho(int pivot,int N,int ind,int M,vector<int>v,long long D,int spec){
if(dep2>=0){
vector<int>v2;
for(auto i:v)
if(dis[ind][i]==dep2)
v2.push_back(i);
v=v2;
}
indd=ind;
sort(v.begin(),v.end(),[](int a,int b){
return pos[indd][a]<pos[indd][b];
});
int l=1,r=v.size()-1,res=1;
while(l<=r){
int mid=l+r>>1;
vector<int>V(M,1);
V[spec]=0;
for(int i=mid;i<v.size();i++) {
if(par[ind][v[i]]!=pivot)
if(!V[pari[ind][par[ind][v[i]]]])
continue;
V[pari[ind][v[i]]]=0;
}
if(ask(V)<D)
l=res=mid+1;
else r=mid-1;
}
int ans=v[res-1];
dep2=actD-dis[ind][ans]-1;
return ans;
}
void find_pair(int N, std::vector<int> U, std::vector<int> V, int A, int B) {
int M=U.size();
for(int i=0;i<M;i++)
adj[U[i]].push_back({V[i],i}),
adj[V[i]].push_back({U[i],i});
long long D=ask(vector<int>(M,0))/A;
int res=M-1,l=1,r=M-1;
actD=D;
while(l<=r){
int mid=l+r>>1;
vector<int>v(M);
for(int i=0;i<mid;i++)
v[i]=1;
if(ask(v)>D*A)
res=r=mid-1;
else l=mid+1;
}
int a=U[res],b=V[res];
bfs(a,0);
bfs(b,1);
vector<int>sta,stb;
for(int i=0;i<N;i++)
if(dis[0][i]<dis[1][i])
sta.push_back(i);
else if(dis[0][i]-dis[1][i])
stb.push_back(i);
answer(whicho(a,N,0,M,sta,D*B-B+A,res),
whicho(b,N,1,M,stb,D*B-B+A,res));
}
