#include "bits/stdc++.h"
using namespace std;
#define int long long
#define pb push_back
#define all(x) ((x).begin(),(x).end())
#define sz(x) ((int)(x).size())
int n;
bool ask(int l,int r){
if(l<1 || r>n) return 0;
cout << "? " << l << " " << r << endl;
bool ans; cin >> ans;
return ans;
}
int search(int l,int r){
if(ask(l,r)==0) return 0;
while(ask(l-1,r+1)){l--;r++;}
return r-l+1;
}
void solve(){
cin >> n;
int ans=1;
for(int i=1;i<=n;i++){
int u = ans/2;
ans=max(ans,search(i-u,i+u+1));
u = (ans+1)/2;
ans=max(ans,search(i-u,i+u));
}
cout << "! " << ans << endl;
}
int32_t main(){
ios::sync_with_stdio(0);cin.tie(0);
int t=1;//cin >> t;
while(t--) solve();
}
