#define here cerr<<"===========================================\n"
#define dbg(x) cerr<<#x<<": "<<x<<endl;
#include <bits/stdc++.h>
#define ld double
#define ll long long
#define ull unsigned long long
#define llinf 100000000000000000LL // 10^17
#define iinf 2000000000 // 2*10^9
#define pb push_back
#define eb emplace_back
#define popb pop_back
#define fi first
#define sc second
#define pii pair<int,int>
#define pll pair<ll,ll>
#define pld pair<ld,ld>
#define all(a) a.begin(),a.end()
#define ceri(a,l,r) {cerr<<#a<<": ";for(ll i_ = l;i_<=r;i_++) cerr<<a[i_]<< " ";cerr<<endl;}
#define cer(a) {cerr<<#a<<": ";for(ll x_ : a) cerr<<x_<< " ";cerr<<endl;}
#define si(a) (ll)(a.size())
using namespace std;
ll n;
bool dbg = 0;
string s;
bool check(ll l,ll r){
l--;
r--;
while(l<=r){
if(s[l]!=s[r]) return 0;
l++;
r--;
}
return 1;
}
bool ask(ll l,ll r){
if(l<1) return 0;
cout<<"? "<<l<< " "<<r<<endl;
bool ans;
if(dbg) return check(l,r);
cin >> ans;
return ans;
}
int main(){
cin >> n;
if(dbg) cin >> s;
ll ans = 1;
for(ll i = 2;i<=n;i++){
if(ask(i-ans-1,i)) ans+=2;
else if(ask(i-ans,i)) ans++;
}
cout<<"! "<<ans<<endl;
return (0-0);
}
