def caesar_cipher(text, key, encrypt=True):
    result = ""
    shift = key if encrypt else -key  # add for encryption, subtract for decryption
    for char in text:
        if char.isalpha():  # only alphabetic characters
            if char.isupper():
                result += chr((ord(char) - ord('A') + shift) % 26 + ord('A'))
            else:
                result += chr((ord(char) - ord('a') + shift) % 26 + ord('a'))
        else:
            result += char  # leave numbers and symbols unchanged
    return result

# ask user for input text
text = input("Enter the text: ")

# ask user for the key
while True:
    try:
        key = int(input("Enter the key (integer): "))
        break
    except ValueError:
        print("Please enter a valid integer.")

# ask user whether to encrypt or decrypt
while True:
    choice = input("Do you want to (E)ncrypt or (D)ecrypt? ").strip().upper()
    if choice in ["E", "D"]:
        encrypting = True if choice == "E" else False
        break
    else:
        print("Please enter 'E' for encryption or 'D' for decryption.")

# process the text
result_text = caesar_cipher(text, key, encrypt=encrypting)

# display the result
print("Result:", result_text)