Fixed-Length Paths I

Given a tree of n nodes, your task is to count the number of distinct paths that consist of exactly k edges. Input The first input line contains two integers n and k: the number of nodes and the path length. The nodes are numbered 1,2,\ldots,n. Then there are n-1 lines describing the edges. Each line contains two integers a and b: there is an edge between nodes a and b. Output Print one integ