Describe a method for performing a card shuffle of a list of 2n elements, by converting it into two lists. A card shuffle is a permutation where a list L is cut into two lists, L₁ and L₂, where L₁ is the first half of L and L₂ is the second half of L, and then these two lists are merged into one by taking the first element in L₁, then the first element in L₂, followed by the second element in L₁, the second element in L₂, and so on.