#include <bits/stdc++.h>

#define x first
#define y second
#define el '\n'
#define debug(x) cout << #x << ": " << x << el
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const int N = 5010, INF = 0x3f3f3f3f, mod = 998244353;

void inc(ll &a, ll b) {
    a += b;
    if (a >= mod) a -= mod;
}

void dec(ll &a, ll b) {
    a -= b;
    if (a < 0) a += mod;
}

ll add(ll a, ll b) {
    a += b;
    return a >= mod ? a - mod : a;
}

ll del(ll a, ll b) {
    a -= b;
    return a < 0 ? a + mod : a;
}

int main() {
    // ios::sync_with_stdio(0); cin.tie(0);
    int n; cin >> n;
    int l = 1, r = n, mid, last = 0;
    while (l < r) {
        mid = l + r >> 1;
        cout << "? " << mid << endl;
        int now; cin >> now;
        if (now == last) {
            cout << "! " << mid << endl;
            return 0;
        }
        if (now > last) l = mid + 1;
        else r = mid - 1;
        last = now;
    }
    cout << "! " << l << endl;
}