# Define the original message to be encoded
message = "Hello, world!"

# Define the rotation value
rotation_value = 3

# Encode the message using the ROL algorithm and the defined rotation value
encoded_message = ""
for char in message:
  if char.isalpha():
    encoded_message += chr((ord(char) - ord("A") + rotation_value) % 26 + ord("A"))
  else:
    encoded_message += char

# Print the resulting encoded message
print(encoded_message)

# Decode the encoded message using the ROL algorithm and the same rotation value
decoded_message = ""
for char in encoded_message:
  if char.isalpha():
    decoded_message += chr((ord(char) - ord("A") - rotation_value) % 26 + ord("A"))
  else:
    decoded_message += char

# Print the resulting decoded message
print(decoded_message)