#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<ll,ll> pl;
typedef pair<int,int> pii;
typedef tuple<int,int,int> tt;
#define all(a) a.begin(), a.end()
#define filter(a) a.erase(unique(all(a)), a.end())
int n;
bool ask (int l, int r) {
assert(1 <= l && l <= r && r <= n);
cout << "? " << l << " " << r << "\n";
cout.flush();
bool ans; cin >> ans;
return ans;
}
void answer (int ans) {
cout << "! " << ans << "\n";
cout.flush();
}
bool okOdd (int sz, int mid) {
return mid - sz / 2 >= 1 && mid + sz / 2 <= n;
}
bool okEven (int sz, int mid) {
return mid - sz / 2 + 1 >= 1 && mid + sz / 2 <= n;
}
int main()
{
ios::sync_with_stdio(0);
cin.tie(0);
cin >> n;
int bestOdd = 1, bestEven = 0;
for (int i = 1; i <= n; i++) {
while (okOdd(bestOdd + 2, i) && ask(i - bestOdd / 2 - 1, i + bestOdd / 2 + 1)) bestOdd += 2;
if (i < n) {
while (okEven(bestEven + 2, i) && ask(i - bestEven / 2, i + bestEven / 2 + 1)) bestEven += 2;
}
}
answer(max(bestOdd, bestEven));
return 0;
}
