#include<bits/stdc++.h>
using namespace std;
//#define int long long
map<pair<int,int>,int>mp;
map<pair<int,int>,int>vis;
int ask(int l,int r){
if(l==r){return 1;}
if(vis[{l,r}]){return mp[{l,r}];}
cout<<"? "<<l<<" "<<r<<endl;
int ret;
vis[{l,r}]=1;
cin>>ret;
mp[{l,r}]=ret;
return ret;
}
int n;
int rpl[300005];
int rask(int l,int r){
if(l==r){return 1;}
if(l%2==1){l++;}
if(r%2==1){r--;}
if(l==r){return 1;}
l=(l+1)/2;r=(r+1)/2;
return ask(l,r);
}
int par[300005];
//*#a#a#a#b#
signed main(){
cin>>n;
int l=1;int r=1;
par[1]=1;
for(int i=2;i<=n+n+1;i++){
if(r<i){
par[i]=0;int lit=i;int rit=i;
while(lit>=1&&rit<=n+n+1&&rask(lit,rit)==1){lit--;rit++;par[i]++;}
}else{
par[i]=min(r-i+1,par[l+(r-i+1)-1])-1;
int lit=i-par[i];int rit=i+par[i];
while(lit>=1&&rit<=n+n+1&&rask(lit,rit)==1){lit--;rit++;par[i]++;}
}
if(i+par[i]-1>r){
r=i+par[i]-1;
l=i-par[i]+1;
}
}
int ans=0;
for(int i=1;i<=n+n+1;i++){
ans=max(ans,par[i]);
}
cout<<"! "<<ans-1<<endl;
}
