#include "prize.h"
#include <bits/stdc++.h>
#define MAX_N 200000
using namespace std;
int N;
bool mark[MAX_N];
vector<int> resp[MAX_N];
int worst=MAX_N;
vector<int> aksp(int x){
if(!mark[x]){
resp[x]=ask(x);
mark[x]=1;
}
return resp[x];
}
int left(int x){
if(!mark[x]){
resp[x]=ask(x);
mark[x]=1;
}
return resp[x][0];
}
int right(int x){
if(!mark[x]){
resp[x]=ask(x);
mark[x]=1;
}
return resp[x][1];
}
int weight(int x){
return left(x)+right(x);
}
int find(int l, int r){
if(l+1>=r){
if(left(l)+right(l)==0){
return l;
}
return -1;
}
if(weight(l)!=weight(r)){
if(weight(l)>weight(r))return find(l, r-1);
else return find(l+1, r);
}
if(left(r)==left(l))return -1;
int mid=(l+r)/2;
int rl=-1, rr=-1;
if(weight(mid)==0)return mid;
rl=find(l, mid);
rr=find(mid, r);
if(rl==-1 && rr==-1)return -1;
else return rl>rr?rl:rr;
}
int easy_solve(int n) {
for(int i = 0; i < n; i++) {
std::vector<int> res = ask(i);
if(res[0] + res[1] == 0)
return i;
}
return 0;
}
void find_worst(){
for(int i=0; i<450; ++i){//Ad hoc
if(left(i)+right(i)<worst){
worst=left(i)+right(i);
if(2*worst>N){
return;
}
}
}
}
int find_best(int n) {
N=n;
if(N<5005)return easy_solve(N);
//find_worst();
return find(0, N);
}
