#include <bits/stdc++.h>
using namespace std;
#define int long long
#define nl endl
#define hehe ios_base::sync_with_stdio(0); cin.tie(NULL); cout.tie(NULL) ;
// const int mod = 998244353;
const int mod = 1e9+7;
const int M = 2e5+5;
int gas(int l, int r){
cout << "? " << l << ' ' << r << nl;
cout.flush();
int x; cin >> x;
return x;
}
void solve(){
int n; cin >> n;
int ans = 1;
for(int i = 2; i <= n-1; i++){
int l = i, r = i;
while(l > 1 && r < n){
if(gas(l-1, r+1) == 1){
l--; r++;
}
else break;
}
ans = max(ans, r - l + 1);
}
for(int i = 1; i <= n-1; i++){
int l = i, r = i+1;
if(gas(l, r) != 1) continue;
while(l > 1 && r < n){
if(gas(l-1, r+1) == 1){
l--; r++;
}
else break;
}
ans = max(ans, r - l + 1);
}
cout << "! " << ans << nl;
}
signed main(){
hehe
// int t; cin >> t;
int t = 1;
while(t--){
solve();
}
return 0;
}
