A tree is a connected graph that doesn't contain any cycles.

The distance between two vertices of a tree is the length (in edges) of the shortest path between these vertices.

You are given a tree with n vertices and a positive number k. Find the number of distinct pairs of the vertices which have a distance of exactly k between them. Note that pairs (v, u) and (u, v) are considered to be the same pair.

The first line contains two integers n and k (1 \le n \le 50000, 1 \le k \le 500) - the number of vertices and the required distance between the vertices.

Next n-1 lines describe the edges as "ai bi" (without the quotes) (1 \le ai,bi \le n, ai \neq bi), where ai and bi are the vertices connected by the i-th edge. All given edges are different.

Print a single integer - the number of distinct pairs of the tree's vertices which have a distance of exactly k between them.

Please do not use the %lld specifier to read or write 64-bit integers in C++. It is preferred to use the cin, cout streams or the %I64d specifier.

In the first sample the pairs of vertexes at distance 2 from each other are (1, 3), (1, 5), (3, 5) and (2, 4).