#include "prize.h"
#include <bits/stdc++.h>
using namespace std;
#define bug(x) cout << #x << " " << x << endl;
#define pii pair<int, int>
map<int, pii> mp;
pii query( int id ){
if( mp.count(id) ) return mp[id];
vector<int> resp = ask(id);
return (mp[id] = pii(resp[0], resp[1]));
}
int solve( int ini, int fim ){
if( query(ini) == query(fim) ) return (( query(ini).first + query(ini).second == 0 ) ? ini : -1 );
int mid = (ini + fim )/2;
int aux = solve( ini, mid );
if( aux != -1 ) return aux;
return solve( mid + 1, fim );
}
int find_best(int n) {
return solve( 0, n - 1 );
}
