N=int(input())
A=list(map(int, input().split()))
mod=10**9+7
if min(A)==0:
    print(-1)
    exit()
D=[1,1,4,729]
d=1
for i in A:
    if i>3:
        print(mod)
        exit()
    else:
        d*=D[i]
    if d>mod:
        print(mod)
        exit()
    
print(mod%d)