#include <bits/stdc++.h>
using namespace std;
using ll=long long;
#define F first
#define S second
#define sz(x) int(x.size())
int n;
signed main() {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
cin >> n;
int L=1;
int neparni=1, parni=0;
for(int i=1; i<=n; i++) {
if(i-L<1 || i+L>n) {
continue;
}
cout << "? " << i-L << ' ' << i+L << '\n';
cout.flush();
int x;
cin >> x;
if(x==1) {
neparni=L*2+1;
L++;
i--;
}
}
L=1;
for(int i=1; i<=n; i++) {
// [i-L, i+L-1]
if(i-L<1 || i+L-1>n) {
continue;
}
cout << "? " << i-L << ' ' << i+L-1 << '\n';
cout.flush();
int x;
cin >> x;
if(x==1) {
parni=L*2;
L++;
i--;
}
}
cout << "! " << max(parni, neparni) << '\n';
cout.flush();
return 0;
}
