b=[1]*((10**7)+1)
b[0]=0
b[1]=0

for i in range(2,(10**7)):
  if b[i]==1:
    for m in range(1,((10**7)+1)):
      if (i+i*m)>10**7:
        break
      else:
        b[i+i*m]=0
        if (i+i*(m+1))>10**7:
          break #bが[0,0,1,1...]の素数リストになったよ！
c=[]
for i in range(2,(10**7)-2):
  if b[i]==1 and b[i+2]==1:
    c.append(i*(i+2))
s=int(input())
import bisect
for i in range(s):
  d=int(input())
  if d <15:
    print(-1)
  else:
    print(c[(bisect.bisect_right(c,d))-1])