lim = pow(10,7)+10
prime = [1 for i in range(lim)]

prime[0] = 0
prime[1] = 0
for i in range(4, lim, 2):
    prime[i] = 0

for i in range(3, lim, 2):
    if prime[i] == 0:
        continue
    if (i*2) > lim:
        continue
    for j in range(i*2, lim, i):
        prime[j] = 0

futago = [15]

for i in range(6, lim, 6):
    if prime[i-1] == 0:
        continue
    if prime[i+1] == 0:
        continue
    futago.append(i*i-1)

# print(futago[:10])
# print(prime[:10])


from bisect import bisect_left, bisect_right


q = int(input())
while q:
    q -= 1

    n = int(input())

    if n < 15:
        print(-1)
        continue
    if n < 35:
        print(15)
        continue
    if n < 143:
        print(35)
        continue

    loc = bisect_right(futago, n)
    print(futago[loc-1])