import bisect

def eratosthenes(n):
    is_prime = ([False, True] * (n//2+1))[0: n+1]
    is_prime[1] = False
    is_prime[2] = True
    for i in range(3, n+1, 2):
        if not(is_prime[i]):
            continue
        if i*i > n:
            break
        for k in range(i*i, n+1, i):
            is_prime[k] = False
    return is_prime

is_prime = eratosthenes(10**7)
multiple_of_twin_prime = []
for i in range(5, 10**7+2):
    if is_prime[i-2] and is_prime[i]:
        multiple_of_twin_prime.append(i*(i-2))

T = int(input())
N = [int(input()) for _ in range(T)]

for n in N:
    i = bisect.bisect(multiple_of_twin_prime, n)
    if i == 0:
        print(-1)
    else:
        print(multiple_of_twin_prime[i-1])