#include <bits/stdc++.h>
#define int long long
#define pb push_back
using namespace std;
const int N=5e5+10;
const int inf=9e18;
const int mod=1e9+7;
pair<int,int>a[N];
signed main() {
ios_base::sync_with_stdio(NULL);
cin.tie(NULL);
int T=1;
// cin>>T;
while(T--) {
int n;
cin>>n;
int l=1,r=3;
int ans=1;
while(r<=n) {
if(l<1) {
l++;
r++;
continue;
}
cout<<"? "<<l<<' '<<r<<endl;
bool x;
cin>>x;
if(x) {
ans=max(ans,r-l+1);
l--;
r++;
continue;
}
r++;
l++;
}
r=ans + 1;
l=1;
while(r<=n) {
if(l<1) {
l++;
r++;
continue;
}
cout<<"? "<<l<<' '<<r<<endl;
bool x;
cin>>x;
if(x) {
ans=max(ans,r-l+1);
l--;
r++;
continue;
}
r++;
l++;
}
cout<<"! "<<ans<<endl;
}
}
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