CS 160, Program 2: Caesar Cipher
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Enter the cipher key [0..25]: 1

1. Encode a message.
2. Decode a message.
3. Quit.
Please enter your menu choice: 1
Enter a sentence to encode: Bozeman, Montana.
Plain:  Bozeman, Montana.
Cipher: 3 16 1 6 14 2 15 , 0 14 16 15 21 2 15 2 . 

1. Encode a message.
2. Decode a message.
3. Quit.
Please enter your menu choice: 2
Enter numbers to decode: 3 16 1 6 14 2 15 , 0 14 16 15 21 2 15 2 .
Cipher: 3 16 1 6 14 2 15 , 0 14 16 15 21 2 15 2 .
Plain:  bozeman, montana.

1. Encode a message.
2. Decode a message.
3. Quit.
Please enter your menu choice: 3

Goodbye.