有 n 个不同的元素，每个元素可以选多次，一共选 k 个元素，有多少种选法？例如，

n=3,k=2 时，有(1,1), (1,2), (1,3), (2,2), (2,3), (3,3), 共 6 种选法。-There are n distinct elements, each element can be selected multiple times, for a total choose k elements, there are many kinds of election law? For example,

n = 3, k = 2, there are (1,1), (1,2), (1,3), (2,2), (2,3), (3,3), a total of six colors method.