MX = 10**9+7

n = int(input())
*a, = map(int, input().split())
if min(a) == 0:
    print(-1)
elif max(a) > 3:
    print(MX)
else:
    v = [1, 4, 729]
    ans = 1
    for ai in a:
        ans *= v[ai-1]
        if ans > MX:
            print(MX)
            break
    else:
        print(MX % ans)