import math, bisect

M = 10**7
isprime = [bool(i%2) for i in range(M+1)]
isprime[1] = False
isprime[2] = True
i = 3
while i <= math.isqrt(M):
    if isprime[i]:
        for j in range(2*i, M+1, i):
            isprime[j] = False
    i += 1

mul_twin_prime = [i*(i+2) for i in range(M-1) if isprime[i] and isprime[i+2]]
T = int(input())
for _ in range(T):
    N = int(input())
    i = bisect.bisect_right(mul_twin_prime, N)
    if i == 0:
        print(-1)
    else:
        print(mul_twin_prime[i-1])