#include <bits/stdc++.h>
using namespace std;
#define ll long long
int main(){
ll n;
cin >> n;
ll len = 1;
auto extend = [&](ll mid){
//get minimum odd and even number > len
//even: gap between mid and mid-1
//odd: mid itself
//cout << "Processing middle at " << mid << "\n";
ll minOdd = (len%2 ? len+2 : len+1);
ll minEven = (len%2 ? len+1 : len+2);
//cout << "Min odd length can extend: " << minOdd << "\n";
//cout << "Min even length can extend: " << minEven << "\n";
ll left1 = mid - (minOdd-1)/2, right1 = mid + (minOdd-1)/2; //for odd
//cout << "For odd length: ";
//cout << left1 << " to. " << right1 << "\n";
ll left2 = mid - (minEven)/2, right2 = mid + (minEven)/2 - 1; //for even
//cout << "For even length: ";
//cout << left2 << " to. " << right2 << "\n";
bool a = false;
if (left1 >= 1 && right1 <= n){
cout << "? " << left1 << " " << right1 << "\n";
cout.flush();
cin >> a;
}
bool b = false;
if (left2 >= 1 && right2 <= n){
cout << "? " << left2 << " " << right2 << "\n";
cout.flush();
cin >> b;
}
if (a && b) return 2LL;
if (a && !b) return minOdd - len;
if (!a && b) return minEven - len;
return 0LL;
};
for (ll i = 2; i <= n; ++i){
while (true){
ll res = extend(i);
//cout << "can extend by " << res << "\n";
if (res == 0) break;
if (len >= n){
cout << "! " << n << "\n";
cout.flush();
return 0;
}
len += res;
}
}
cout << "! " << len << "\n";
cout.flush();
}
