# encryption and Decryption software

import base64

def encrypt(key, clear):

    enc = []

    for i in range(len(clear)):

        key_c = key[i % len(key)]

        enc_c = chr((ord(clear[i]) + ord(key_c)) % 256)

        enc.append(enc_c)

    return base64.urlsafe_b64encode("".join(enc).encode()).decode()

def decrypt(key, enc):

    dec = []

    enc = base64.urlsafe_b64decode(enc).decode()

    for i in range(len(enc)):

        key_c = key[i % len(key)]

        dec_c = chr((256 + ord(enc[i]) - ord(key_c)) % 256)

        dec.append(dec_c)

    return "".join(dec)

def main():

    while True:

        choice = input("Do you want to (e)ncrypt or (d)ecrypt? ").lower()

        if choice in ('e', 'd'):

            break

        else:

            print("Invalid choice. Please enter 'e' or 'd'.")

    key = input("Enter the key: ")

    text = input("Enter the text: ")

    if choice == 'e':

        encrypted_text = encrypt(key, text)

        print("Encrypted text:", encrypted_text)

    else:

        decrypted_text = decrypt(key, text)

        print("Decrypted text:", decrypted_text)

if __name__ == "__main__":

    main()