/*
Idea:
- http://ioi2017.org/tasks/editorial/prize.pdf
*/
#include "prize.h"
#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define INF (1 << 30)
#define MOD (1000 * 1000 * 1000 + 7)
#define maxn 201111
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
map<int, pii> m[maxn];
int ans;
pii ASK(int x){
vector<int> v = ask(x);
return mp(v[0], v[1]);
}
void solve(int l, int d){
if(ans != -1 || l > d)
return;
int mid = (l + d) / 2;
pii cur = ASK(mid);
int sum = cur.fi + cur.se;
if(sum == 0){
ans = mid;
return;
}
auto it = m[sum].upper_bound(mid);
bool left = 1, right = 1;
if(it != m[sum].begin()){
it--;
if(cur.se == it -> se.se)
left = 0;
it++;
}
if(it != m[sum].end()){
if(cur.se == it -> se.se)
right = 0;
}
m[sum][mid] = cur;
if(left)
solve(l, mid - 1);
if(right)
solve(mid + 1, d);
}
int find_best(int n){
ans = -1;
solve(0, n - 1);
return ans;
}
