n, *a = map(int, open(0).read().split())
mx = max(a)
mn = min(a)

mod = 10 ** 9 + 7

if mx > 3:
    print(mod)
elif mn == 0:
    print(-1)
else:
    b = [0, 1, 16, 729]
    ans = 1
    for c in a:
        ans *= b[c]
        if ans > mod:
            print(mod)
    print(mod % ans)