For building the encrypted string:Take every 2nd char from the string, then the other chars, that are not every 2nd char, and concat them as new String.
Do this n times!
Examples:
```
"This is a test!", 1 -> "hsi  etTi sats!"
"This is a test!", 2 -> "hsi  etTi sats!" -> "s eT ashi tist!"
```
Write two methods:
```python
def encrypt(text, n)
def decrypt(encrypted_text, n)
```
```Fsharp
let encrypt (str:string) (n:int) -> string
let decrypt (str:string) (n:int) -> string
```
For both methods:
If the input-string is null or empty return exactly this value!
If n is <= 0 then return the input text.
This kata is part of the Simple Encryption Series:
Simple Encryption #1 - Alternating Split
Simple Encryption #2 - Index-Difference
Simple Encryption #3 - Turn The Bits Around
Simple Encryption #4 - Qwerty
Have fun coding it and please don't forget to vote and rank this kata! :-)
def decrypt(text, n):
    if text:
        mid = len(text) // 2
        for _ in range(n):
            text = ''.join(sum(zip(text[mid:], list(text[:mid]) + ['']), ()))
    return text


def encrypt(text, n):
    if text:
        for _ in range(n):
            text = text[1::2] + text[::2]
    return text
def decrypt(text, n):
    if text:
        mid = len(text) // 2
        for _ in range(n):
            text = ''.join(sum(zip(text[mid:], list(text[:mid]) + ['']), ()))
    return text


def encrypt(text, n):
    if text:
        for _ in range(n):
            text = text[1::2] + text[::2]
    return text