# Define the substitution key
key = "C X Y B W P R V Q J Z M N T K E L D F G H I O U S"

# Define the plaintext and ciphertext functions
def encrypt(message,dic):
    ciphertext = ""
    for char in message:
        if char.isalpha():
            # Check if char is uppercase or lowercase
            if char.isupper():
                # Convert to lowercase and encrypt using key
                encrypted = key[ord(char) - ord("A")].lower()
            else:
                # Convert to uppercase and encrypt using key
                encrypted = key[ord(char) - ord("a")].upper()
            ciphertext += encrypted
    return ciphertext

def decrypt(message,dic):
    plaintext = ""
    for char in message:
        if char.isalpha():
            # Check if char is uppercase or lowercase
            if char.isupper():
                # Convert to lowercase and decrypt using inverse key
                decrypted = key[25 - key.index(char.lower())].upper()
            else:
                # Convert to uppercase and decrypt using inverse key
                decrypted = key[25 - key.index(char)].lower()
            plaintext += decrypted
    return plaintext