from bisect import*
t=int(input())
N=10000000
spf=[0]*(N+1)
prime=[]
for m in range(2,N+1):
 if spf[m]<1:spf[m]=m;prime+=[m]
 for p in prime:
  if p>spf[m] or p*m>N:break
  spf[p*m]=p
ans=[]
for i,j in zip(prime,prime[1:]):
  if i+2==j:
    ans+=i*j,
ans=[-1]+sorted(ans)
for _ in range(t):
  n=int(input())
  i=bisect(ans,n)-1
  print(ans[i])