from math import isqrt from functools import cache import sys sys.setrecursionlimit(10**7) lim = 10**7 + 10 prime_flag = [1]*lim prime_flag[0] = 0 prime_flag[1] = 0 for p in range(2,lim): if prime_flag[p]: for q in range(2*p,lim,p): prime_flag[q] = 0 @cache def search(x): if prime_flag[x]&prime_flag[x+2]: return x*(x+2) return search(x-1) t = int(input()) for i in range(t): n = int(input()) if n <= 14: print(-1) continue print(search(isqrt(n+1)-1))