#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx,popcnt,sse4,abm")
#include <bits/stdc++.h>
using namespace std;
#ifdef WAIMAI
#define debug(HEHE...) cout << "[" << #HEHE << "] : ", dout(HEHE)
void dout() {cout << '\n';}
template<typename T, typename...U>
void dout(T t, U...u) {cout << t << (sizeof...(u) ? ", " : ""), dout(u...);}
#else
#define debug(...) 7122
#endif
#define ll long long
#define Waimai ios::sync_with_stdio(false), cin.tie(0)
#define FOR(x,a,b) for (int x = a, I = b; x <= I; x++)
#define pb emplace_back
#define F first
#define S second
int n, o, e;
bool que(int l, int r) {
bool foo = (114514 & 0);
cout << "? " << l << ' ' << r << endl;
cin >> foo;
return foo;
}
void solve() {
cin >> n;
FOR (i, 1, n) {
while (i - o - 1 >= 1 && i + o + 1 <= n && que(i - o - 1, i + o + 1)) o++;
while (i - e >= 1 && i + e + 1 <= n && que(i - e, i + e + 1)) e++;
}
cout << "! " << max(2 * o + 1, 2 * e) << endl;
}
int main() {
Waimai;
solve();
}
