#include<bits/stdc++.h>
using namespace std;
#define int long long
int s = 0;
int pre = 0;
void beizeng(int start, int end) {
	int now = 1;
	int shuru;
	while (1) {
		if (now > end) {
			s += now / 2;
			beizeng(now / 2+1, end);
			return;
		}
		cout << '?' << ' ' << s+now << endl;
		cin >> shuru;
		if (shuru == pre) {
			cout << '!' << ' ' << s+now << endl;
			return;
		}
		else if (shuru > pre) {
			pre = shuru;
			now *= 2;
		}
		else {
			s += now / 2;
			pre = shuru;
			beizeng(now / 2+1, now-1);
			return;
		}
	}
}
signed main() {
	int n;
	cin >> n;
	beizeng(1, n);
}