#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 a, int b){
cout << "? " << a << ' ' << b << nl;
cout.flush();
int x;
if(!(cin >> x)){
exit(0);
}
return x;
}
void solve(){
int n; cin >> n;
if(n == 1){
cout << "! " << 1 << nl;
return;
}
int ans = 1;
int l = 1;
int r = 3;
while(r <= n){
if(l <= 0) { l++; r++; }
else{
if(gas(l,r)){
ans = max(ans, r - l + 1);
l--; r++;
}
else{
l++;r++;
}
}
}
l = 1, r = 2;
while(r <= n){
if(l <= 0) { l++; r++; }
else{
if(gas(l,r)){
ans = max(ans, r-l+1);
l--; r++;
}
else{
l++, r++;
}
}
}
cout << "! " << ans << nl;
}
signed main(){
hehe
// int t; cin >> t;
int t = 1;
while(t--){
solve();
}
return 0;
}
