#include "prize.h"
#define here cerr<<"===========================================\n"
#define dbg(x) cerr<<#x<<": "<<x<<endl;
#include "bits/stdc++.h"
//#include <ext/pb_ds/tree_policy.hpp>
//#include <ext/pb_ds/assoc_container.hpp>
#define ld double
#define ll int
#define llinf 100000000000000000LL // 10^17
#define pb push_back
#define popb pop_back
#define fi first
#define sc second
#define endl '\n'
#define pll pair<ll,ll>
#define pld pair<ld,ld>
#define sz(a) (ll)(a.size())
#define all(a) a.begin(),a.end()
#define ceri(a,l,r) {cerr<<#a<<": ";for(ll i_ = l;i_<=r;i_++) cerr<<a[i_]<< " ";cerr<<endl;}
#define cer(a) {cerr<<#a<<": ";for(ll x_ : a) cerr<<x_<< " ";cerr<<endl;}
#define daj_mi_malo_vremena ios_base::sync_with_stdio(false);cerr.tie(0);cout.tie(0);cin.tie(0);
using namespace std;
#define maxn 200005
ll n;
ll ans = -1;
ll a[maxn][2],val[maxn];
set<ll> s[maxn];
void get(ll i){
vector<ll> v = ask(i);
a[i][0] = v[0],a[i][1] = v[1];
val[i] = a[i][0] + a[i][1];
}
void reshi(ll l,ll r){
if(l>r||(ans!=-1)) return;
ll mid = (l+r)/2;
get(mid);
if(val[mid]==0){
ans = mid;
return;
}
ll sum = val[mid];
auto it = s[sum].upper_bound(mid);
ll lok = 1,rok = 1;
if(it!=s[sum].end()){
ll j = *it;
if(j>r&&a[j][0]-a[mid][0]==0) rok = 0;
}
if(it!=s[sum].begin()){
it--;
ll j = *it;
if(j<l&&a[mid][0]-a[j][0]==0) lok = 0;
}
s[sum].insert(mid);
if(lok) reshi(l,mid-1);
if(rok) reshi(mid+1,r);
}
int find_best(int N){
n = N;
reshi(0,n-1);
return ans;
}
/*
8
3 1 3 2 3 3 2 3
*/
