1a: caesar_decipher(c1a, 8)
1b: caesar_decipher(c1b, 14)
2a: affine_decipher(c2a, 3, 3, True)
2b: caesar_decipher(c2b, 6)
3a: affine_decipher(c3a, 7, 8, True)
3b: keyword_decipher(c3b, 'louvigny', 2)
4a: keyword_decipher(c4a, 'montal', 2)
4b: keyword_decipher(c4b, 'salvation', 2)