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

current = 0

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

minimum = current
nextSub = k

for i in range(1, n):
    plus = n - max(nextSub - 1, i) + i - (nextSub - k)
    minus = n - plus
    current += (plus - minus) * 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
            nextSub += 1
        else:
            break
    
    minimum = min(minimum, current)

print(minimum)