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

dp = [[float("inf") for _ in range(k + 1)] for _ in range(n)]
for i in range(0, k + 1):
    dp[0][i] = 0
for i in range(n):
    for j in range(1, k + 1):
        if i + j < n:
            # dp[i + j][j] = min(dp[i + j][j], dp[i][j] + abs(heights[i] - heights[i + j]))
            val1 = dp[i + j][j]
            val2 = dp[i][0] + abs(heights[i] - heights[i + j])
            if val2 < val1:
                dp[i + j][j] = val2
                if dp[i + j][0] > val2:
                    dp[i + j][0] = val2
        # if i == 0 and j == 1:
        #     print("here")
        #     print(dp[i][j], abs(heights[i] - heights[i + j]))
# result = float("inf")
# for i in range(1, k + 1):
#     result = min(result, dp[-1][i])
# print(result)
# print(dp)
print(dp[-1][0])

Fixed submission:
#!/usr/bin/env python
from __future__ import division, print_function

import os
import sys
from io import BytesIO, IOBase

if sys.version_info[0] < 3:
    from __builtin__ import xrange as range
    from future_builtins import ascii, filter, hex, map, oct, zip


def main():
    n, k = map(int, input().split())
    heights = [int(x) for x in input().split()]

    dp = [[float("inf") for _ in range(k + 1)] for _ in range(n)]
    for i in range(0, k + 1):
        dp[0][i] = 0
    for i in range(n):
        for j in range(1, k + 1):
            if i + j < n:
                # dp[i + j][j] = min(dp[i + j][j], dp[i][j] + abs(heights[i] - heights[i + j]))
                val1 = dp[i + j][j]
                val2 = dp[i][0] + abs(heights[i] - heights[i + j])
                if val2 < val1:
                    dp[i + j][j] = val2
                    if dp[i + j][0] > val2:
                        dp[i + j][0] = val2
            # if i == 0 and j == 1:
            #     print("here")
            #     print(dp[i][j], abs(heights[i] - heights[i + j]))
    # result = float("inf")
    # for i in range(1, k + 1):
    #     result = min(result, dp[-1][i])
    # print(result)
    # print(dp)
    print(dp[-1][0])


# region fastio

BUFSIZE = 8192


class FastIO(IOBase):
    newlines = 0

    def __init__(self, file):
        self._fd = file.fileno()
        self.buffer = BytesIO()
        self.writable = "x" in file.mode or "r" not in file.mode
        self.write = self.buffer.write if self.writable else None

    def read(self):
        while True:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            if not b:
                break
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines = 0
        return self.buffer.read()

    def readline(self):
        while self.newlines == 0:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            self.newlines = b.count(b"\n") + (not b)
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines -= 1
        return self.buffer.readline()

    def flush(self):
        if self.writable:
            os.write(self._fd, self.buffer.getvalue())
            self.buffer.truncate(0), self.buffer.seek(0)


class IOWrapper(IOBase):
    def __init__(self, file):
        self.buffer = FastIO(file)
        self.flush = self.buffer.flush
        self.writable = self.buffer.writable
        self.write = lambda s: self.buffer.write(s.encode("ascii"))
        self.read = lambda: self.buffer.read().decode("ascii")
        self.readline = lambda: self.buffer.readline().decode("ascii")


def print(*args, **kwargs):
    """Prints the values to a stream, or to sys.stdout by default."""
    sep, file = kwargs.pop("sep", " "), kwargs.pop("file", sys.stdout)
    at_start = True
    for x in args:
        if not at_start:
            file.write(sep)
        file.write(str(x))
        at_start = False
    file.write(kwargs.pop("end", "\n"))
    if kwargs.pop("flush", False):
        file.flush()


if sys.version_info[0] < 3:
    sys.stdin, sys.stdout = FastIO(sys.stdin), FastIO(sys.stdout)
else:
    sys.stdin, sys.stdout = IOWrapper(sys.stdin), IOWrapper(sys.stdout)

input = lambda: sys.stdin.readline().rstrip("\r\n")

# endregion

if __name__ == "__main__":
    main()