#include <iostream>
using namespace std;

int print(int x)
{
    cout << "? " << x << endl;
    cout.flush();
    cin >> x;
    return x;
}


int main() {

    int n;
    cin >> n;
    int low=1,high=n,mid;
    while(low<high)
    {
        mid=(low+high)/2;
        if(print(mid)<print(mid+1)) high=mid;
        else low=mid+1;
    }
    cout << "! " << low << endl;
    cout.flush();
    return 0;
}
