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

if min(A) == 0:
    print(-1)
elif max(A) >= 4:
    print(1000000007)
else:
    res = 1
    p = [1, 4, 729]
    for i in range(N):
        res *= p[A[i] - 1]
        if res > 1000000007:
            print(1000000007)
            break
    else:
        print(1000000007 % res)