MOD = 10 ** 9 + 7
n = int(input())
a = list(map(int, input().split()))
if 0 in a:
    print(-1)
else:
    ans = 1
    for x in a:
        if x >= 4:
            print(MOD)
            break
        f = 1
        for i in range(x):
            f *= (i + 1)
        for i in range(f):
            ans *= x
        if ans > MOD:
            print(MOD)
            break
    else:
        print(MOD % ans)