This mission is the part of set. Another one - Caesar cipher encryptor.
Oh no! When we received an encrypted text we've noticed that there are some extra symbols!
Your mission is to decrypt a secret message (which consists of text, the whitespace characters and special chars like "!", "&", "?" etc.) using Caesar cipher where each letter is replaced by another that stands at a fixed distance. For example ("a b c", 3) == "d e f". Also you should ignore/delete all special characters. So the message like this ("!d! [e] &f*", -3) will be decrypted just as "a b c" and nothing more.
Input: A Secret message as a string (lowercase letters only, white spaces and special characters)
Output: The same string, but decrypted into a normal text
to_decrypt("!d! [e] &f*", -3) == "a b...