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 $|40-70|+|70-70|+|70-60|=40$.