// #include <bits/stdc++.h> #include <iostream> #include <cmath> #include <algorithm> #include <map> #include <vector> #include <iomanip> #include <string> #include <queue> #include <set> #include <deque> #include <numeric> #include <stack> #include <chrono> using namespace std; void fast_io(){ // freopen("", "r", stdin); // freopen("", "w", stdout); ios::sync_with_stdio(0); cin.tie(); cout.tie(); cout << setprecision(9); } #define int long long // #define endl '\n' #define all(v) (v).begin(), (v).end() #define rall(v) (v).rbegin(), (v).rend() #define fi first #define se second int n; bool query(int l, int r){ cout << "? " << l << ' ' << r << endl; int x; cin >> x; return x; } void solve() { int ans = 1; cin >> n; for (int i = 1; i <= n; i++){ if (ans % 2 == 0){ int l = i - ans / 2, r = i + ans / 2; while (l > 0 && r <= n){ int x = query(l, r); if (x) ans = max(ans, r - l + 1); else break; l--, r++; } } else { int l = i - (ans + 1) / 2, r = i + (ans + 1) / 2; while (l > 0 && r <= n){ int x = query(l, r); if (x) ans = max(ans, r - l + 1); else break; l--, r++; } } int l = i - ans / 2, r = i + ans / 2 + 1; while (l > 0 && r <= n){ int x = query(l, r); if (x) ans = max(ans, r - l + 1); else break; l--, r++; } } cout << "! " << ans << endl; return; } signed main() { fast_io(); srand(chrono::steady_clock::now().time_since_epoch().count()); int tc = 1; // cin >> tc; while (tc--) solve(); return 0; }