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

#define ll long long
#define ld long double
#define F first
#define S second
#define all(v) v.begin(),v.end()
#define sz(v) (int)v.size()
#define precision cout << fixed << setprecision(15);

const int inf = 1e9;
const long long INF = 1e18;
const int mod = 1e9 + 7;
const int bit32 = log2(inf) + 3;
const int bit64 = log2(INF) + 3;

mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
clock_t time_p = clock();

void ktj() {
  time_p = clock() - time_p;
  cerr << "Time elapsed : " << (float)(time_p)/CLOCKS_PER_SEC << "\n";
}

void pre() {}

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

  auto ask = [=](int L, int R) {
    cout << "? " << L << ' ' << R << endl;
    int result; cin >> result;
    return result;
  };

  auto output = [=](int x) {
    cout << "! " << x << endl;
    exit(0);
  };

  int L = 1, R = n;
  int p = ask(L, R);
  if (n == 2) {
    output(3 - p);
  }

  auto maxPos = [=] (int L, int R, int pos) mutable {
    int ans = 1;
    while (L < R) {
      int M = (L + R) / 2;
      if (M == L or M == R) {
        output(L + R - ask(L, R));
      }
      p = ask(M, pos);
      if (p == pos) {
        L = M; ans = M;
      } else {
        R = M - 1;
      }
    }
    output(ans);
  };

  auto minPos = [=] (int L, int R, int pos) mutable {
    int ans = n;
    while (L < R) {
      int M = (L + R) / 2;
      if (M == L or M == R) {
        output(L + R - ask(L, R));
      }
      p = ask(pos, M);
      if (p == pos) {
        R = M; ans = M;
      } else {
        L = M + 1;
      }
    }
    output(ans);
  };

  if (p == L) {
    minPos(L, R, p);
  } else if (p == R) {
    maxPos(L, R, p);
  } else {
    int x = ask(L, p);
    if (x == p) {
      maxPos(L, p, p);
    } else {
      minPos(p, R, p);
    }
  }
}

#define GOOGLE 0
#define MULTIPLE_TC 0

int32_t main() {

  ios_base::sync_with_stdio(false);
  cin.tie(NULL);cout.tie(NULL); 

  pre();

  int t = 1, T;

  if (MULTIPLE_TC)
    cin >> t;

  for (T = 1; T <= t; T++) {
    if (GOOGLE)
      cout << "Case #" << T << ": ";
    solve();
  }

  ktj();
}