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

if max(A)>=4:
    print(10**9+7)
    exit()

T=[0,1,4,729]
X=1
for a in A:
    X*=T[a]
    if X>=10**9+8:
        break

if X==0:
    print(-1)
else:
    print((10**9+7)%X)