from bisect import bisect_right
P = list(range(10**7+1))
for i in range(2,10**7+1):
    if i*i>10**7:break
    for j in range(i*i,10**7+1,i):
        P[j] = P[i]
Q = []
for i in range(2,10**7+1):
    if P[i]==i and i+2<10**7 and P[i+2]==i+2:
        Q.append(i)
T = int(input())
for _ in range(T):
    N = int(input())
    ind = bisect_right(Q,N**0.5)
    if ind-1>=0 and Q[ind-1]*(Q[ind-1]+2)<=N:
        print(Q[ind-1]*(Q[ind-1]+2))
    elif ind-2>=0 and Q[ind-2]*(Q[ind-2]+2)<=N:
        print(Q[ind-2]*(Q[ind-2]+2))
    else:
        print(-1)