There are ~N~ stones, numbered ~1, 2, \dots, N~. For each ~i~ ~(1 \le i \le 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, \dots, 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 \le N \le 10^5~
• ~1 \le K \le 100~
• ~1 \le h_i \le 10^4~

Input Specification

The first line of input will contain 2 integers ~N~ and ~K~.

The second line of input will contain ~N~ spaced integers, ~h_i~, the height of stone ~i~.

Output Specification

Output a single integer, the minimum possible total cost incurred.

Sample Input 1

5 3
10 30 40 50 20

Sample Output 1

30

Sample Input 2

3 1
10 20 10

Sample Output 2

20

Sample Input 3

2 100
10 10

Sample Output 3

0

Sample Input 4

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

Sample Output 4

40

Sample Explanations

For the first sample, if we follow the path ~1 \to 2 \to 5~, the total cost incurred would be ~|10-30| + |30-20| = 30~.

For the second sample, if we follow the path ~1 \to 2 \to 3~, the total cost incurred would be ~|10-20| + |20-10| = 20~.

For the third sample, if we follow the path ~1 \to 2~, the total cost incurred would be ~|10-10| = 0~.

For the fourth sample, if we follow the path ~1 \to 4 \to 8 \to 10~, the total cost incurred would be ~|40-70| + |70-70| + |70-60| = 40~.