#ifdef __AVX2__
#pragma GCC target "avx2"
#endif
#pragma GCC optimize "O3"
#pragma GCC optimize "unroll-loops"
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
using namespace std;
#define int long long
#define elif else if
#define all(l) begin(l),end(l)
#define rall(l) rbegin(l),rend(l)
#define append push_back
#define print(l) for(auto i:l) cout<<i<<' '; cout<<endl;
#define pprint(a,b) cout<<a<<' '<<b<<endl;
#define inp(l) for(auto &i:l) cin>>i;
#define ordered_set tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update>
#define pai make_pair
// #define endl "\n"
#define pii pair<int,int>
#define fi first
#define se second
#define vec vector
// const int mod=998244353;
const int mod1=998244353;
const int mod=1e9+7;
const int N=2e5+5;
// string s;
// bool qu(int l,int r){
// string a;
// for(int i=l-1;i<=r-1;i++) a+=s[i];
// string b=a;
// reverse(all(b));
// return a==b;
// }
int iter=1,itera=1;
void solve(){
int n;
cin>>n;
// cin>>s;
int ans=0;
for(int i=1;i<=n;i++){
while(1){
int l,r;
int x=ans+2;
if(x%2){
l=i-x/2;
r=i+x/2;
}
else{
l=i-x/2+1;
r=i+x/2;
}
if(l<1 or r>n)
break;
cout<<"? "<<l<<' '<<r<<endl;
int f;
// f=qu(l,r);
cin>>f;
// cout<<l<<' '<<r<<' '<<f<<endl;
if(f) ans=x;
else break;
}
}
int ans1=1;
for(int i=1;i<=n;i++){
while(1){
int l,r;
int x=ans1+2;
if(x%2){
l=i-x/2;
r=i+x/2;
}
else{
l=i-x/2+1;
r=i+x/2;
}
if(l<1 or r>n)
break;
cout<<"? "<<l<<' '<<r<<endl;
int f;
cin>>f;
// f=qu(l,r);
// cout<<l<<' '<<r<<' '<<f<<endl;
if(f) ans1=x;
else break;
}
}
// cout<<"ans "<<ans<<' '<<ans1<<endl;
cout<<"! "<<max(ans,ans1)<<endl;
}
signed main(){
// freopen("","r",stdin);
// freopen("","w",stdout);
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
cout<<fixed<<setprecision(20);
// cin>>itera;
for(iter=1;iter<=itera;iter++) solve();
}
