#include <bits/stdc++.h>
using namespace std;

int main() {
	int N, K; cin >> N >> K;
	
	auto is_good = [&](int x) -> bool {
		for (int d = 1; d * d <= x; d++) {
			if (x%d) continue;
			if (d <= K and x / d <= K) return false;
		}
		return true;
	};
	
	for (int x = N; x >= max(1, N - 281); x--) {
		if (is_good(x)) {
			cout << x << endl;
			return 0;
		}
	}
	cout << -1 << endl;
}