import bisect

def make_twin_prime_products(limit, prod_limit):
    is_prime = [True] * (limit + 1)
    is_prime[0] = is_prime[1] = False

    for i in range(2, int(limit**0.5) + 1):
        if is_prime[i]:
            for j in range(i*i, limit + 1, i):
                is_prime[j] = False

    twin_products = []
    for i in range(2, limit - 1):
        if is_prime[i] and is_prime[i+2]:
            prod = i * (i+2)
            if prod > prod_limit:
                break
            twin_products.append(prod)

    return twin_products

MAX_N = 10**14
prime_limit = int((MAX_N)**0.5) + 100
p_L = make_twin_prime_products(prime_limit, MAX_N)

T = int(input())
for _ in range(T):
    N = int(input())
    idx = bisect.bisect_left(p_L, N)
    if idx < len(p_L) and p_L[idx] == N:
        print(N)
    else:
        if idx == 0:
            print(-1)
        elif idx == len(p_L):
            print(p_L[idx - 1])
        else:
            print(p_L[idx - 1])