Reference: CaesarCipher
CaesarCipher(str, n) transforms the string str using the Caesar cipher, i.e. shifts all English letters n steps to the right along the alphabet (modulo 26). CaesarCipher(str) assumes n = 3, and the inverse of str ↦ CaesarCipher(str, n) is str ↦ CaesarCipher(str, -n).