def prime_factors(n):
    ans = []
    i = 2
    while i * i <= n:
        while n % i == 0:
            ans.append(i)
            n //= i
        i += 1
    if n > 1:
        ans.append(n)
    return ans


t = int(input())
for _ in range(t):
    n, k = map(int, input().split())
    if n == k:
        print(-1)
        continue
    for i in range(n, 0, -1):
        ps = prime_factors(i)
        if len(ps) == 1:
            if ps[0] <= k:
                print(-1)
            else:
                print(ps[0])
            break
        else:
            a = 1
            b = 1
            for i in range(len(ps) - 1, -1, -1):
                if a > b:
                    b *= ps[i]
                else:
                    a *= ps[i]
            if a > k or b > k:
                print(a * b)
                break