There are ~N~ stones in a line with the ~i~-th stone having a height of ~a_i~.

There is a toad who is initially on the first stone. He will repeat the following action some number of times to reach the last stone:

• If the toad is currently on stone ~i~, jump to any one of stone ~i+1~, ~i+2~, ~...~, ~i+k~. Here, a cost of ~|a_i - a_j|~ is incurred, where ~a_j~ is the stone the toad lands on.

Find the minimum total cost required for the toad to reach the last stone.

Constraints

For all subtasks,

~2 \le N \le 10^5~

~1 \le a_i, k \le 100~

Subtask 1 [50%]

~k = 2~

Subtask 2 [50%]

No additional constraints.

Input Specification

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

The next line will contain ~N~ space-separated integers ~a_i~.

Output Specification

Output one integer, the minimum total cost required for the toad to reach the last stone.

Sample Input

6 2
1 5 4 5 2 5

Sample Output

4

Explanation for Sample Output

The toad can jump from stone ~1~ to stone ~2~, then to stone ~4~ and finally to stone ~6~.