N = int(input())
A = [int(a) for a in input().split()]
X = [0, 1, 4, 729]
P = 10 ** 9 + 7
if min(A) == 0:
    print(-1)
else:
    s = 1
    for a in A:
        if a > 3:
            print(P)
            break
        s *= X[a]
        if s > P:
            print(P)
            break
    else:
        print(P % s)