//#pragma GCC optimize("O3,unroll-loops")
//#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
/*
ID: samikgo1
TASK: wormhole
LANG: C++
*/
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll,ll> pll;
#define all(x) x.begin(),x.end()
#define allr(x) x.rbegin(),x.rend()
//#define f first
//#define s second
//#define x first
//#define y second
const int INF = 1e9;
const ll modulo = 1e9 + 7;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
//#include <ext/pb_ds/assoc_container.hpp>
//#include <ext/pb_ds/tree_policy.hpp>
//using namespace __gnu_pbds;
//#define ordered_set tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update>
#define int ll
int n;
bool check(int l,int r){
if(l<1 or r>n)return false;
cout << "? " << l << ' ' << r << endl;
int a;cin>>a;
return a==1;
}
int bin_search(int l,int r){
if(!check(l,r))return 0;
while(true){
if(check(l-1,r+1)){l--;r++;}
else break;
}
return r-l+1;
}
void solve(){
cin>>n;
int ans = 1;
for(int i=1;i<=n;i++){
ans = max(ans, bin_search(i-ans/2,i+1+ans/2));
ans = max(ans, bin_search(i-ans/2-(ans%2),i+ans/2+(ans%2)));
}
cout << "! " << ans << '\n';
}
int32_t main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
// freopen("in.txt","r",stdin);
// freopen("out.txt","w",stdout);
// int t;
// cin >> t;
// while(t--)
// for(int i=1;i<=1000;i++){
// if(encode2(i)>110)cout << i << ' ';
// }
// cout << endl;
solve();
}
