C++ ::  Decrypting And Encrypting Following A Certain Protocol?

I have a certain method of encrypting text. You get the first character of the word. For example in the word "hacker", you get 'h', and then you get the last character 'r'. The encrypted word until now is "hr". Then we get the same word with the 'h' and 'r' removed, now it's "acke". I do the same thing and get the first character 'a' and the last one 'e' and them to the encrypted word: it is now "hrae".

The left letters of the word are "ck", again we do the same thing and take the first character 'c' and the last character 'k' and and add them to the new encrypted word so it is "hraeck". The above word has an even number of characters and at the end had 2 characters left 'c' and 'k',first and last, in some cases of words with an odd number of characters, only one character is left! I'm completely lost on how to encrypt and decrypt this.