Author: Amzuloiu Andrei-Ciprian
Requires: python 3.x, regex
Input: input_decrypt.txt and input_encrypt.txt files. The key is read from the command line.
Output: output.txt file
Options: 1 - Encrypt the text from input_encrypt.txt using a given key. 2 - Decrypt the text from input_decrypt.txt using a given key.