The Vigenere Cipher. This cipher was used as recently as the Civil War by the Confederate forces. The key
is slightly more complex than the Caesar Cipher. Vigenere used the number of letters after 'A' for his key.
For example, if the key = COD, the first letter in the cypher is shifted 2 characters (because "C" is 2 letters
after the letter 'A'), the second letter is shifted 14 letters (O being 14 letters after 'A'), and the third letter
is shifted 3 letters (D being 3 letters after 'A'). Then the pattern is repeated for subsequent letters.
I
Decrypt the following message which has a-key = COD: YSPGSWCHGCKQ
