import typing

class FenwickTree:
    '''Reference: https://en.wikipedia.org/wiki/Fenwick_tree'''

    def __init__(self, n: int = 0) -> None:
        self._n = n
        self.data = [0] * n

    def add(self, p: int, x: typing.Any) -> None:
        assert 0 <= p < self._n

        p += 1
        while p <= self._n:
            self.data[p - 1] += x
            p += p & -p

    def sum(self, left: int, right: int) -> typing.Any:
        assert 0 <= left <= right <= self._n

        return self._sum(right) - self._sum(left)

    def _sum(self, r: int) -> typing.Any:
        s = 0
        while r > 0:
            s += self.data[r - 1]
            r -= r & -r

        return s

n, k = map(int, input().split())
a = list(map(int, input().split()))
bit = FenwickTree(n)

current = 0

for i in range(n):
    if i < k:
        current += abs(a[i] - a[0])
        bit.add(i, 1)
    else:
        current -= abs(a[i] - a[0])
        bit.add(i, -1)

minimum = current
nextSub = k

for i in range(1, n):
    plus = -bit.sum(i, n) + bit.sum(0, i)
    current += plus * abs(a[i] - a[i - 1])

    while nextSub < n:
        left = a[nextSub - k]
        right = a[nextSub]
        leftDiff = abs(left - a[i])
        rightDiff = abs(right - a[i])

        if leftDiff > rightDiff:
            current -= 2 * leftDiff
            current += 2 * rightDiff
            bit.add(nextSub, 2)
            bit.add(nextSub - k, -2)
            nextSub += 1
        else:
            break
    
    minimum = min(minimum, current)

print(minimum)