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 resource
import sys
#resource.setrlimit(resource.RLIMIT_STACK, [0x100000000, resource.RLIM_INFINITY])
#threading.Thread(target=main).start()
import threading
threading.stack_size(2**26)
sys.setrecursionlimit(10**8)
mod=(10**9)+7
#fact=[1]
#for i in range(1,1000001):
#    fact.append((fact[-1]*i)%mod)
#ifact=[0]*1000001
#ifact[1000000]=pow(fact[1000000],mod-2,mod)
#for i in range(1000000,0,-1):
#    ifact[i-1]=(i*ifact[i])%mod
from sys import stdin, stdout
from bisect import bisect_left as bl
from bisect import bisect_right as br
import itertools
import math
import heapq
from random import randint as rn
from Queue import Queue as Q
def modinv(n,p):
    return pow(n,p-2,p)
def ncr(n,r,p):
    t=((fact[n])*((ifact[r]*ifact[n-r])%p))%p
    return t
def ain():
    return map(int,sin().split())
def sin():
    return stdin.readline().strip()
def GCD(x, y):
   while(y):
       x, y = y, x % y
   return x
"""**************************************************************************"""
n,k=ain()
h=ain()
d=[10**18]*n
d[0]=0
for i in range(1,n):
    for j in range(1,min(k+1,i+1)):
        d[i]=min(d[i-j]+abs(h[i]-h[i-j]),d[i])
print d[-1]
