T = int(input())
NK = [tuple(map(int, input().split())) for _ in range(T)]

# エラトステネスの篩
def eratos(n):
    primes = [True] * (n+1)
    primes[0], primes[1] = False, False
    for i in range(2, int(n**0.5)+1):
        if primes[i]:
            for j in range(i**2, n+1, i):
                primes[j] = False
    primes[1] = True
    ret = [num for num, is_prime in enumerate(primes) if is_prime]
    return ret

def is_prime(i):
    if i <= 1:
        return False
    for j in range(2, int(i**0.5) + 1):
        if i % j == 0:
            return False
    return True

P = eratos(10 ** 5)

for N,K in NK:

    ans = 0
    for a in P:
        b = N//a
        # print(a,b)
        if a <= K and b <= K:continue
        if is_prime(b):
            ans = max(ans,a*b)

    print(ans if ans != 0 else -1)