Write a program that produces a Caesar cipher of a given message string. A Caesar cipher, or rotation cipher, is formed by rotating each letter of a message by a given amount. For example, if you rotate by 3, every A becomes D; every B becomes E; and so on. Toward the end of the alphabet, you wrap around: X becomes A; Y becomes B; and Z becomes C. Your program should prompt for a message and an amount by which to rotate each letter and should output the encoded message.

Your message? Attack zerg at dawn
Encoding key? 3
Your message: DWWDFN CHUJ DW GDZQ