#### Running Key Cipher

I
```"""
https://en.wikipedia.org/wiki/Running_key_cipher
"""

def running_key_encrypt(key: str, plaintext: str) -> str:
"""
Encrypts the plaintext using the Running Key Cipher.

:param key: The running key (long piece of text).
:param plaintext: The plaintext to be encrypted.
:return: The ciphertext.
"""
plaintext = plaintext.replace(" ", "").upper()
key = key.replace(" ", "").upper()
key_length = len(key)
ciphertext = []
ord_a = ord("A")

for i, char in enumerate(plaintext):
p = ord(char) - ord_a
k = ord(key[i % key_length]) - ord_a
c = (p + k) % 26
ciphertext.append(chr(c + ord_a))

return "".join(ciphertext)

def running_key_decrypt(key: str, ciphertext: str) -> str:
"""
Decrypts the ciphertext using the Running Key Cipher.

:param key: The running key (long piece of text).
:param ciphertext: The ciphertext to be decrypted.
:return: The plaintext.
"""
ciphertext = ciphertext.replace(" ", "").upper()
key = key.replace(" ", "").upper()
key_length = len(key)
plaintext = []
ord_a = ord("A")

for i, char in enumerate(ciphertext):
c = ord(char) - ord_a
k = ord(key[i % key_length]) - ord_a
p = (c - k) % 26
plaintext.append(chr(p + ord_a))

return "".join(plaintext)

def test_running_key_encrypt() -> None:
"""
>>> key = "How does the duck know that? said Victor"
>>> ciphertext = running_key_encrypt(key, "DEFEND THIS")
>>> running_key_decrypt(key, ciphertext) == "DEFENDTHIS"
True
"""

if __name__ == "__main__":
import doctest

doctest.testmod()
test_running_key_encrypt()

plaintext = input("Enter the plaintext: ").upper()
print(f"\n{plaintext = }")

key = "How does the duck know that? said Victor"
encrypted_text = running_key_encrypt(key, plaintext)
print(f"{encrypted_text = }")

decrypted_text = running_key_decrypt(key, encrypted_text)
print(f"{decrypted_text = }")
```