#include <bits/stdc++.h>
using namespace std;
#define forn(i, n) for (int i = 0; i < int(n); i++)
#define forsn(i, s, n) for (int i = int(s); i < int(n); i++)
#define dforn(i, n) for (int i = int(n) - 1; i >= 0; i--)
#define dforsn(i, s, n) for (int i = int(n) - 1; i >= int(s); i--)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x.size())
using vi = vector<int>;
using ll = long long;
#define pb push_back
#define eb emplace_back
#define fst first
#define snd second
vi ask(int i);
map<int, vi> memo;
bool found = false;
int maxi;
vi query(int i) {
if (found) return {maxi, maxi};
if (memo.count(i)) return memo[i];
return memo[i] = ask(i);
}
int querySum(int i) {
vi a = query(i);
if (a[0] + a[1] == 0) found = true;
return a[0] + a[1];
}
const int K = 450;
void solve(int lo, int hi, int s, int e) {
if (s == e || found) return;
if (lo == hi) {
query(lo);
return;
}
int mid = (lo + hi) / 2;
while (!found && mid >= lo && querySum(mid) < maxi) mid--;
if (mid >= lo) {
solve(lo, mid, s, query(mid)[0]);
solve((lo + hi) / 2 + 1, hi, query(mid)[0] + (lo + hi) / 2 - mid, e);
} else {
solve((lo + hi) / 2 + 1, hi, s + mid - lo + 1, e);
}
}
int find_best(int n) {
maxi = 0;
forn(i, min(K, n)) {
maxi = max(maxi, querySum(i));
if ((maxi * maxi + 1LL) * (maxi * maxi + 1LL) + 1LL > n) break;
if (found) break;
}
int lo = 0, hi = n - 1;
while (!found && querySum(lo) != maxi) lo++;
while (!found && querySum(hi) != maxi) hi--;
solve(lo, hi, query(lo)[0], query(hi)[0]);
for (auto [i, a] : memo) {
if (a[0] + a[1] == 0) return i;
}
assert(false);
}
