#include <bits/stdc++.h>
using namespace std ;

#define ff    first
#define ss    second
#define pb    push_back

typedef long long    ll;
typedef pair<ll,ll>    ii;
typedef long double    lf;


mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());

const ll SQ = 320;
const ll N = 3e5+5;
const ll mod = 998244353;
const ll oo = 1e9+5;

int ask (int x) {
  cout << "? " << x << endl;
  cin >> x;
  return x;
}

int main(){
  #ifdef LOCAL
//  freopen("input.txt","r",stdin);
  #endif // LOCAL
  ios_base::sync_with_stdio(0);
  cin.tie(0);cout.tie(0);

  int n; cin >> n;
  int l = 1, r = n;

  if (ask(1) == 0) {
    cout << "! " << 1 << endl;
    return 0;
  }

  while (l + 1 < r) {
    int mi = (l + r) / 2;
    int g = ask(mi);
    if (g == 0) {
      l++;
      r = mi - 1;
      if (ask(l) == 0) {
        cout << "! " << l << endl;
        return 0;
      }
    }
    else if (g == 2) {
      l = mi;
      if (ask(r) == 2) {
        cout << "! " << r << endl;
        return 0;
      }
      r--;
    }
    else {
      cout << "! " << mi << endl;
      return 0;
    }
  }
  cout << "! " << r << endl;
  return 0;
}