I am writing a very easy encryption program. I just shift the ASCII order number of a sign with a key. My code looks as following:

```
#Type in sign or text and key
clear_text = input("Text? ")
key = int(input("Key? "))

# saves ASCII order number of the sign
ord_number = ord(clear_text)

#shift ASCII odernumber with the key -> encryption
shift_ord_number = ord_number + key
key_ord_number = chr(shift_ord_number)
print(key_ord_number)

```

I want to advance this code by being able to type in a whole sentence. For this I somehow must detect how many signs the user has typed in. How would that be possible? And what loops would you recommend?