#include <bits/stdc++.h>
using namespace std;
#define int long long
int n;
bool chck(int i, int sz) {
int l = (sz % 2 == 1) ? i - sz / 2 : i - sz / 2 + 1, r = i + sz / 2;
if (min(l, r) < 1 || max(l, r) > n) return false;
cout << "? " << l << " " << r << endl;
bool ans; cin >> ans;
return ans;
}
void cmp() {
// Start sz at 2, even first
int sz = 1, ans = 0;
for (int i = 1; i <= n; i++) {
while (true) {
if (!chck(i, sz)) break;
ans = sz, sz += 2;
}
}
sz = ans + 1;
for (int i = 1; i <= n; i++) {
while (true) {
if (!chck(i, sz)) break;
ans = sz, sz += 2;
}
}
cout << "! " << ans << endl;
exit(0);
}
signed main() {
cin >> n;
cmp();
}
