#include<stdio.h>
void solve()
{
	long long int n, k;
	scanf("%lld %lld", &n, &k);
	long long int i, f;
	for (; n > k; n--)
	{
		f = 0;
		for (i = k; i * k >= n && f == 0; i--)
			if (n % i == 0)
				f++;
		if (f == 0)
		{
			printf("%lld\n", n);
			return;
		}
	}
	printf("-1\n");
	return;
}
int main()
{
	int t;
	scanf("%d", &t);
	for (; t > 0; t--)
		solve();
	return 0;
}