from bisect import bisect_right

T = int(input())
M = 10**7

isprime = [True] * (M+1)
isprime[0] = isprime[1] = False
for i in range(2, M-1):
	for j in range(i*i, M+1, i):
		isprime[j] = False

twin = []
for i in range(M+1):
	if isprime[i] and isprime[i+2]:
		twin.append(i*(i+2))

for _ in range(T):
	n = int(input())
	if n < 15: 
		print(-1)
		continue
	idx = bisect_right(twin, n)
	print(twin[idx-1])