$)$ Carer cup Persons A and B uses an encryption based system for their conversation.

Each conversation message is encoded from the source and decoded in

the destination using a shared private positive number key known to each other.

The algorithm is illustrated with an example.

Input Format with explanation:

$1.$ Operation $(1$ for Encoding and $2$ for Decoding$)$

$2.$ Input message

$3.$ Input private key