//
// Created by watemus on 07.02.2021.
//
 
#ifdef LOCAL
#define _GLIBCXX_DEBUG
#endif
 
#include <bits/stdc++.h>
 
using namespace std;
 
#define ALL(a) a.begin(), a.end()
#define RALL(a) a.rbegin(), a.rend()
#define FF first
#define SS second
 
using ll = long long;
using ld = long double;
 
#define int ll
 
template<typename T>
using vec = std::vector<T>;
 
template<typename T>
using uset = std::unordered_set<T>;
 
template<typename T1, typename T2>
using umap = std::unordered_map<T1, T2>;
 
constexpr ll INFL = 1000000000000000069;
constexpr int INFI = 1000000069;
const ld PI = acos(-1);
 
#ifdef LOCAL
std::mt19937 rnd(69);
#else
std::mt19937 rnd(std::chrono::steady_clock::now().time_since_epoch().count());
#endif
 
vec<pair<int, int>> DD = {{1, 0}, {-1, 0}, {0, 1}, {0, -1}};
 
#ifdef LOCAL
#else
#endif
 
void run() {
  int n;
  cin >> n;
  auto ask = [&](int i) {
    if (i == 0 || i == n + 1)
      return INFL;
    cout << "? " << i << endl;
    int ans;
    cin >> ans;
    return ans;
  };
  auto check = [&](int i) {
    int a1 = ask(i - 1);
    int a2 = ask(i);
    int a3 = ask(i + 1);
    if (a1 < a2 && a2 < a3) {
      return -1;
    } else if (a1 > a2 && a2 > a3) {
      return 1;
    } else if (a1 > a2 && a2 < a3) {
      cout << "! " << i << endl;
      exit(0);
    } else {
      return -1;
    }
  };
  int l = 1;
  int r = n + 1;
  while (l + 1 < r) {
    int mid = (l + r) / 2;
    int val = check(mid);
    if (val == -1) {
      r = mid;
    } else {
      l = mid;
    }
  }
  cout << "! ";
  cout << l << endl;
}
 
signed main() {
#ifdef LOCAL
//  std::freopen("input.txt", "r", stdin);
#else
  std::ios_base::sync_with_stdio(false);
  std::cin.tie(nullptr);
#endif
  int t = 1;
  // cin >> t;
  while (t--) {
    run();
  }
  return 0;
}
 