import bisect

def eratosthenes(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*i, n+1, i):
                primes[j] = False

    return [p for p in range(2, n+1) if primes[p]]

tbl = eratosthenes(10**7)
twins = []
for i in range(len(tbl) - 1):
    l, r = tbl[i], tbl[i+1]
    if l+2 == r:
        twins.append(l*r)

t = int(input())
for _ in range(t):
    n = int(input())
    p = bisect_right(twins, n)
    if 1 <= p:
        print(twins[p-1])
    else:
        print(-1)