#include <bits/stdc++.h>
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2")
#define int long long
#define pii pair<int,int>
#define vi vector<int>
#define ff first
#define ss second
#define sp << " " <<
#define all(x) x.begin(),x.end()
#define big(x) ((int)(x.size()))
using namespace std;
const int MOD = 1e9+7, LIM = 1e6+1, inf = 2e9;
const int N = 1e5+1;
int n;
map<pii,int> mp;
int ctr = 0;
int ask(int l,int r) {
if (l == r) return 1;
if (l < 1 || r > n) return 0;
if (mp.count({l,r})) return mp[{l,r}];
cout << "?" sp l sp r << endl;
int x;
cin >> x;
return mp[{l,r}] = x;
}
void solve() {
cin >> n;
int mx1 = 1,mx2 = 0;
for (int i=1;i<=n;i++) {
if (ask(i-mx1/2-1,i+mx1/2+1)) {
mx1+=2;
while (mx1 < n && ask(i-mx1/2-1,i+mx1/2+1)) mx1+=2;
}
if (ask(i-mx2/2,i+1+mx2/2)) {
mx2+=2;
while (mx2 < n && ask(i-mx2/2,i+1+mx2/2)) mx2+=2;
}
}
cout << "!" sp max(mx1,mx2) << endl;
}
signed main() {
ios_base::sync_with_stdio(0); cin.tie(0);
#ifdef Dodi
freopen("in.txt", "r", stdin);
freopen("out.txt", "w", stdout);
#endif
int t = 1;
//cin >> t;
while (t --> 0) solve();
}
