#include <bits/stdc++.h>

using namespace std;

#define int long long
//#define ll long long
#define double long double
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()

const int INF = 2e16;

void solve() {
	int n;
	cin >> n;
	
	int id;
	cout << "? 1 " << n << endl;
	cin >> id;
	
	int l = 0;
	int r = n;
	while (r - l > 1) {
		int m = (l + r) >> 1;
		int ll = max(1LL, id - m);
		int rr = min(n, id + m);
		cout << "? " << ll << " " << rr << endl;
		int x;
		cin >> x;
		if (x == id) r = m;
		else l = m;
	}
	
	int ans = 0;
	if (id - r <= 0) {
		ans = id + r;
	}
	else if (id + r > n) {
		ans = id - r;
	}
	else {
		cout << "? " << id - r << " " << id << endl;
		int x;
		cin >> x;
		if (x == id) {
			ans = id - r;
		}
		else {
			ans = id + r;
		}
	}
	cout << "! " << ans << endl;
}
	

signed main() {
	ios_base::sync_with_stdio(false);
	cin.tie(0); cout.tie(0);
	srand(time(0));
	int t = 1;
	//cin >> t;
	while (t--) solve();
}