N=int(input())
*A,=map(int, input().split())
mod=10**9+7

if min(A)==0:
    print(-1)
    exit()

pattern=[0,1,2**2,3**6]
ans=1
for a in A:
    if a>3:
        print(mod)
        exit()
    else:
        ans*=pattern[a]
    if ans>mod:
        print(mod)
        exit()
    
print(mod%ans)