Jon Snow knows nothing

In an epic battle between two lovers Jon Snow and Ygritte, you have been summoned to decide the victor. Ygritte wants to prove in front of entire Westeros that Jon Snow knows nothing. She gives Jon a string S in which she has performed N swaps. Jon has to find the original string and emerge victorious. One swap is performed in this way: - ith letter from the end is placed between ith and (i+1)th