SP22560 RTREE2 - Valid Path

Roger was having fun solving his problems until he found this one. As you know, an undirected connected graph with **N** nodes and **N-1** edges is called a tree. You are given an integer **'K'** and a tree consisting of **'N'** nodes. Each node **'i'** has a value **a(i)** associated with it. We call a path **'P'** of tree valid if following conditions are satisfied: - **P** has at least 2 nodes associated with it. - **Max a(u) - Min a(u) >= K** (u belongs to the nodes present in the choosen P). Your task is to count the number of Valid Paths.

The first line contains two space-separated integers **N** and **K**. The second line contains **N** space-separated positive integers **a(1), a(2), ..., a(n).** Then the next **n - 1** line each contains a pair of integers **u** and **v** denoting that there is an edge between u and v.

Print the number of Valid Paths.