mod = 10**9 + 7

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

if min(A) == 0:
    print(-1)
    exit()
if max(A) > 3:
    print(mod)
    exit()

ans = 1
B = [0, 1, 2**2, 3**6]

for a in A:
    ans *= B[a]
    if ans > mod:
        print(mod)
        exit()

print(mod%ans)