Transpozicijski kod - dešifriranje

cypher = "SIFRAT"
decypher = ""
key_length = int(input("Enter key length:"))
x = int(input('Enter key:'))
key = [int(i) for i in str(x)]

n = len(cypher)//len(key)

for i in range(0, len(cypher), n):
    print(cypher[i:i+n])

print('')
for j in range(0, n):
    for k in range(0, len(key)):
        decypher+=cypher[(key[k]-1)*n+j]

print("Decyphered: ", decypher)