```\n/**\n*  @param a - a list of non null integers, in ascending order\n*  @param b - a list of non null integers, in ascending order\n*  @return the integers that are contained in either a or b, in ascending order\n*/\n\nList<Integer> union(List<Integer> a, List<Integer> b);\n```\n\nFollow up: Given access to multicore processor, how would you implment the same function so that we can do an union faster (in terms of time complexity)\nHint: split the inputs to perform union and merge them back in O(1) time.

\n/**\n*  @param a - a list of non null integers, in ascending order\n*  @param b - a list of non null integers, in ascending order\n*  @return the integers tha