/*
Author: Matin Alizadeh - Maliza88
They're one person :)
*/
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef string str;
#define IOS ios::sync_with_stdio(false); cin.tie(0); cout.tie(0)
#define endl '\n'
#define YES "YES"
#define NO "NO"
#define NoSolution "No solution"
const ll MOD = 1e9 + 7;
int n;
void solve() {
cin >> n;
int R = n + 1, L = 0;
for (; ; ) {
int mid = (R + L) / 2, ask;
cout << '?' << ' ' << mid << endl;
cin >> ask;
if (ask == 0) {
cout << '=' << ' ' << mid << endl;
return;
}
if (ask == 1) {
L = mid;
continue;
}
R = mid;
}
}
int main() {
IOS;
solve();
return 0;
}
