Reference to solution provided here: https://stackoverflow.com/a/9231458
I need to do this in reverse, e.g.:
A E F G H I B J K L M N C O P Q R S D T U V W X
to
A E A F A G A H A I B J B K B L B M B N C O C P C Q C R C S D T D U D V D W D X
Can someone please help me?