6834.Fixed-Length Paths II

Time Limit: 1s Memory Limit: 512MB

Given a tree of $n$ nodes, your task is to count the number of distinct paths that have at least $k_1$ and at most $k_2$ edges.

Input Format(From the terminal/stdin)

The first input line contains three integers $n$ , $k_1$ and $k_2$ : the number of nodes and the path lengths. 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 $b$ .

  • $1 \le k_1 \le k_2 \le n \le 2 \cdot 10^5$
  • $1 \le a,b \le n$

Output Format(To the terminal/stdout)

Print one integer: the number of paths.

Sample Input

Copy
5 2 3
1 2
2 3
3 4
3 5
 · · \n
 · \n
 · \n
 · \n
 · \n

Sample Output

Copy
6
 \n
Source: CSES, Tree Algorithms, 2081

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