import java.util.Scanner;

public class Main {
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		int t = sc.nextInt();
		label:
		for (int z = 0; z < t; z++) {
			int n = sc.nextInt();
			int k = sc.nextInt();

			if (n <= k) {
				System.out.println(-1);
				continue;
			}
			for (int v = n; v > k; v--) {
				boolean flg = false;
				for (int i = 2; i <= k && i * i <= v; i++) {
					if (v % i == 0 && v / i <= k) {
						flg = true;
						break;
					}
				}
				if (!flg) {
					System.out.println(v);
					continue label;
				}
			}
			System.out.println(-1);
		}
		sc.close();
	}
}