P=[]
def sieve_of_eratosthenes(n):
  prime = [True for i in range(n+1)]
  p = 2
  while (p * p <= n):
    if (prime[p] == True):
      for i in range(p * 2, n+1, p):
        prime[i] = False
    p += 1
  for p in range(2, n):
    if prime[p]:
      P.append(p)
sieve_of_eratosthenes(10**7)
L=[]
for i in range(len(P)-1):
	if P[i]+2==P[i+1]:
		L.append(P[i]*P[i+1])

import bisect
t=int(input())
for _ in range(t):
	n=int(input())
	if n<15:
		print(-1)
	else:
		id=bisect.bisect_right(L,n)
		print(L[id-1])