MOD = 10 ** 9 + 7

N = int(input())
A = list(map(int, input().split()))

ans = 1
for a in A:
    if a == 0:
        print(-1)
        exit()
    elif a == 2:
        ans *= 4
    elif a == 3:
        ans *= 729
    elif a >= 4:
        print(MOD)
        exit()

    if ans > MOD:
        print(MOD)
        exit()
print(MOD % ans)