Let L be some regular language in which all the words happen to have an even length. Let us de fine the new language Twist(L) to be the set of all the words of L twisted, where by twisted we mean the first and second letters have been interchanged, the third and fourth letters have been interchanged, and so on. For example, if

           L = {ba abba babb ... }
Twist(L) = {ab baab abbb ... }

Build a PDA that accepts Twist(L)