There are N stones, numbered 1, 2, \ldots, N. For each i (1 \leq i \leq N), the height of Stone i is h_i.

There is a frog who is initially on Stone 1. He will repeat the following action some number of times to reach Stone N:

* If the frog is currently on Stone i, jump to one of the following: Stone i + 1, i + 2, \ldots, i + K. Here, a cost of |h_i - h_j| is incurred, where j is the stone to land on.



Find the minimum possible total cost incurred before the frog reaches Stone N.

Constraints

* All values in input are integers.
* 2 \leq N \leq 10^5
* 1 \leq K \leq 100
* 1 \leq h_i \leq 10^4

Input

Input is given from Standard Input in the following format:


N K
h_1 h_2 \ldots h_N


Output

Print the minimum possible total cost incurred.

Examples

Input

5 3
10 30 40 50 20


Output

30


Input

3 1
10 20 10


Output

20


Input

2 100
10 10


Output

0


Input

10 4
40 10 20 70 80 10 20 70 80 60


Output

40
import java.util.Scanner;
public class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int s = sc.nextInt();
		int[] a = new int[n];
		int[] b = new int[n];
		
		for(int i = 0; i<n; i++){
			a[i] = sc.nextInt();
			b[i]=1000000000;
		}
		b[0]=0;
		for(int i = 0; i<n; i++){
			for(int j = 1; j<=s; j++){
				if(i+j<=n-1){
				if(b[i+j]>(Math.abs(a[i]-a[i+j])+b[i])){
					b[i+j]=(Math.abs(a[i]-a[i+j])+b[i]);
				}
				}
			}
		}
		System.out.println(b[n-1]);
	}
}