#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define ull unsigned long long
#define db double
#define pii pair<int,int>
#define pli pair<ll,int>
#define pil pair<int,ll>
#define pll pair<ll,ll>
#define ti3 tuple<int,int,int>
#define mat vector<vector<int>>
const int inf = 1 << 30;
const ll linf = 1LL << 62;
const db EPS = 1e-7;
template<class T> void chmin(T& x, T y){if(x > y) x = y;}
template<class T> void chmax(T& x, T y){if(x < y) x = y;}

void solve(){
    int n;
    cin >> n;

    int l = 1, r = n, sec;
    cout << "?" << " " << l << " " << r << endl;
    cout.flush();
    cin >> sec;

    if(l != sec){
        int nxt;
        cout << "?" << " " << l << " " << sec << endl;
        cout.flush();
        cin >> nxt;
        if(nxt == sec){
            l = sec;
            for(int i = 16; i >= 0; i--){
                if(l - (1 << i) < 1) continue;
                cout << "? " << l - (1 << i) << " " << sec << endl;
                cout.flush();
                cin >> nxt;
                if(nxt != sec) l -= 1 << i;
            }
            cout << "! " << l - 1 << endl;
            cout.flush();
            return;
        }
    }
    if(r != sec){
        int nxt;
        r = sec;
        for(int i = 16; i >= 0; i--){
            if(r + (1 << i) > n) continue;
            cout << "? " << sec << " " << r + (1 << i) << endl;
            cout.flush();
            cin >> nxt;
            if(nxt != sec) r += 1 << i;
        }
        cout << "! " << r + 1 << endl;
        cout.flush();
        return;
    }
}

int main(){
    solve();
    return 0;
}