#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx,popcnt,sse4,abm")
#include <bits/stdc++.h>
using namespace std;
#ifdef WAIMAI
#define debug(HEHE...) cout << "[" << #HEHE << "] : ", dout(HEHE)
void dout() {cout << '\n';}
template<typename T, typename...U>
void dout(T t, U...u) {cout << t << (sizeof...(u) ? ", " : ""), dout(u...);}
#else
#define debug(...) 7122
#endif
#define ll long long
#define Waimai ios::sync_with_stdio(false), cin.tie(0)
#define FOR(x,a,b) for (int x = a, I = b; x <= I; x++)
#define pb emplace_back
#define F first
#define S second
const int SIZE = 2e5 + 5;
int n;
int z[SIZE];
int que(int l, int r) {
if (l & 1) return 1;
int foo = 114514;
l /= 2, r /= 2;
cout << "? " << l << ' ' << r << endl;
cin >> foo;
return foo;
}
void solve() {
cin >> n;
n = 2 * n + 1;
for (int i = 1, mid = 0, r = 0; i <= n; i++) {
if (i <= r) {
z[i] = min(z[2 * mid - i], r - i);
if (i + z[i] < r) continue;
if (i + z[2 * mid - i] > r) continue;
}
int len = min(i - 1, n - i);
for (int j = z[i] + 1; j <= len; j++) {
if (que(i - j, i + j) == 0) break;
z[i]++;
}
if (i + z[i] > r) {
mid = i;
r = i + z[i];
}
}
cout << "! " << *max_element(z + 1, z + n + 1) << '\n';
}
int main() {
Waimai;
solve();
}
