## https://yukicoder.me/problems/no/3127

import math

def main():
    T = int(input())
    questions = []
    for _ in range(T):
        N = int(input())
        questions.append(N)

    max_n = max(questions)

    sqrt_n = int(math.sqrt(max_n))

    is_prime = [True] * (sqrt_n + 10)
    for p in range(2, sqrt_n + 10):
        if not is_prime[p]:
            continue

        x = 2 * p
        while x <= sqrt_n + 9:
            is_prime[x] = False
            x += p
    
    d_prime = []
    for p in range(2, sqrt_n + 1):
        if is_prime[p] and is_prime[p + 2]:
            d_prime.append(p)
    
    for n in questions:
        if d_prime[0] * (d_prime[0] + 2) > n:
            print(-1)
            continue

        low = 0
        high = len(d_prime) - 1
        while high - low > 1:
            mid = (high + low) // 2
            if d_prime[mid] * (d_prime[mid] + 2) <= n:
                low = mid
            else:
                high = mid

        if d_prime[high] * (d_prime[high] + 2) <= n:
            print(d_prime[high] * (d_prime[high] + 2))
        else:
            print(d_prime[low] * (d_prime[low] + 2))



    













                


if __name__ == "__main__":
    main()