n=int(input())
arr=list(map(int,input().split()))
if arr.count(0)!=0:
    print(-1)
elif arr.count(1)+arr.count(2)+arr.count(3)!=n:
    print(10**9+7)
else:
    mod=10**9+7
    ans=1
    for val in arr:
        if val==1:
            ans*=1
        elif val==2:
            ans*=4
            ans%=mod
        elif val==3:
            ans*=729
            ans%=mod
    print(ans)