#include "prize.h"
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int,int> pi;
typedef vector <int> vi;
typedef vector <pi> vpi;
typedef pair<pi, ll> pii;
typedef set <ll> si;
typedef long double ld;
#define f first
#define s second
#define mp make_pair
#define FOR(i,s,e) for(int i=s;i<=int(e);++i)
#define DEC(i,s,e) for(int i=s;i>=int(e);--i)
#define pb push_back
#define all(x) (x).begin(), (x).end()
#define lbd(x, y) lower_bound(all(x), y)
#define ubd(x, y) upper_bound(all(x), y)
#define aFOR(i,x) for (auto i: x)
#define mem(x,i) memset(x,i,sizeof x)
#define fast ios_base::sync_with_stdio(false),cin.tie(0),cout.tie(0)
#define maxn 200010
#define INF (ll)1e9
#define MOD 1000000007
typedef pair <vi, int> pvi;
typedef pair <int,pi> ipi;
typedef vector <pii> vpii;
int N;
vi memo[maxn];
bool queried[maxn];
int sm[maxn];
vi query(int x){
if (queried[x]) return memo[x];
queried[x] = 1;
memo[x] = ask(x);
sm[x] = memo[x][0] + memo[x][1];
return memo[x];
}
bool done = 0;
int dnc(int l,int r){
if (done || l > r) return -1;
if (l == r){
query(l);
if (sm[l] == 0) return l;
return -1;
}
query(l); query(r);
if (sm[r] == sm[l] && memo[l][0] == memo[r][0]) return -1;
int m = (l+r)/2;
return max(dnc(l,m), dnc(m+1,r));
}
const int sqrtn = 472;
int find_best(int n) {
N = n;
return dnc(0,N-1);
}
