Buggy python submission (verdict: Time Limit Exceeded):
N, K = map(int, input().split())
h = list(map(int, input().split()))
 
DP = [0]
for i in range(N-1):
    act = float("inf")
    for k in range(K):
        if i-k < 0 : continue
        act = min(DP[-1-k] + abs(h[i-k]-h[i+1]) , act)
    DP += [act]
 
print(DP[-1])

Fixed submission:
import sys
import math
from decimal import Decimal, ROUND_HALF_UP, ROUND_HALF_EVEN
from collections import deque
from bisect import bisect_left
from itertools import product
def I(): return int(sys.stdin.readline())
def MI(): return map(int, sys.stdin.readline().split())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LI2(N): return [list(map(int, sys.stdin.readline().split())) for i in range(N)]
#文字列を一文字ずつ数字に変換、'5678'を[5,6,7,8]とできる
def LSI(): return list(map(int, list(sys.stdin.readline().rstrip())))
def LSI2(N): return [list(map(int, list(sys.stdin.readline().rstrip()))) for i in range(N)]
#文字列として取得
def ST(): return sys.stdin.readline().rstrip()
def LST(): return sys.stdin.readline().rstrip().split()
def LST2(N): return [sys.stdin.readline().rstrip().split() for i in range(N)]
def FILL(i,h): return [i for j in range(h)]
def FILL2(i,h,w): return [FILL(i,w) for j in range(h)]
def FILL3(i,h,w,d): return [FILL2(i,w,d) for j in range(h)]
def FILL4(i,h,w,d,d2): return [FILL3(i,w,d,d2) for j in range(h)]
def sisha(num,digit): return Decimal(str(num)).quantize(Decimal(digit),rounding=ROUND_HALF_UP)
#'0.01'や'1E1'などで指定、整数に戻すならintをかます
MOD = 1000000007
INF = float("inf")
sys.setrecursionlimit(10**6+10)

N, K= MI()
S = [0]+LI()
S += [0]
dp = [INF]*(N+5)
dp[1] = 0
for i in range(N):
    for j in range(1,K+1):
        if i+j <= N:
            dp[i+j] = min(dp[i+j],dp[i] + abs(S[i+j]-S[i]))
print(dp[N])

Buggy python submission (verdict: Time Limit Exceeded):
n,K = map(int,input().split())
v = [int(x) for x in input().split()]

dp = [float("inf") for i in range(n+10)]
dp[0] = 0
dp[1] = abs(v[1]-v[0])
for i in range(n-2):
    for k in range(K):
        if i+1-k>=0:
            dp[i+2] = min(dp[i+2],dp[i+1-k]+abs(v[i+2]-v[i+1-k]))


print(dp[n-1])

Fixed submission:
import sys
import math
from decimal import Decimal, ROUND_HALF_UP, ROUND_HALF_EVEN
from collections import deque
from bisect import bisect_left
from itertools import product
def I(): return int(sys.stdin.readline())
def MI(): return map(int, sys.stdin.readline().split())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LI2(N): return [list(map(int, sys.stdin.readline().split())) for i in range(N)]
#文字列を一文字ずつ数字に変換、'5678'を[5,6,7,8]とできる
def LSI(): return list(map(int, list(sys.stdin.readline().rstrip())))
def LSI2(N): return [list(map(int, list(sys.stdin.readline().rstrip()))) for i in range(N)]
#文字列として取得
def ST(): return sys.stdin.readline().rstrip()
def LST(): return sys.stdin.readline().rstrip().split()
def LST2(N): return [sys.stdin.readline().rstrip().split() for i in range(N)]
def FILL(i,h): return [i for j in range(h)]
def FILL2(i,h,w): return [FILL(i,w) for j in range(h)]
def FILL3(i,h,w,d): return [FILL2(i,w,d) for j in range(h)]
def FILL4(i,h,w,d,d2): return [FILL3(i,w,d,d2) for j in range(h)]
def sisha(num,digit): return Decimal(str(num)).quantize(Decimal(digit),rounding=ROUND_HALF_UP)
#'0.01'や'1E1'などで指定、整数に戻すならintをかます
MOD = 1000000007
INF = float("inf")
sys.setrecursionlimit(10**6+10)

N, K= MI()
S = [0]+LI()
S += [0]
dp = [INF]*(N+5)
dp[1] = 0
for i in range(N):
    for j in range(1,K+1):
        if i+j <= N:
            dp[i+j] = min(dp[i+j],dp[i] + abs(S[i+j]-S[i]))
print(dp[N])