#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <atcoder/modint>
using namespace std;
using i32 = int;
using u32 = unsigned int;
using i64 = long long;
using u64 = unsigned long long;
#define rep(i,n) for(int i=0; i<(int)(n); i++)
const i64 INF = 1001001001001001001;

using Modint = atcoder::static_modint<998244353>;

int main(){
    int N; cin >> N;
    int ans = N-1;
    for(int i=0; i<N/2; i++){
        int u = i*2, v = i*2+1;
        cout << "? " << u << " " << v << endl;
        int res; cin >> res;
        if(res == u){ ans = v; break; }
        if(res == v){ ans = u; break; }
    }
    cout << "! " << ans << endl;
    return 0;
}



struct ios_do_not_sync{
    ios_do_not_sync(){
        ios::sync_with_stdio(false);
        cin.tie(nullptr);
    }
} ios_do_not_sync_instance;