from collections import defaultdict

N, K = map(int, input().split())
A = list(map(int, input().split()))

ans = 1e17
lo, hi = min(A), max(A)
while lo <= hi:
    l = (2*lo + hi)//3
    h = (lo + 2*hi)//3
    s_l = min_l = sum(abs(A[j] - l) for j in range(K))
    for j in range(K, N):
        s_l = s_l - abs(A[j - K] - l) + abs(A[j] - l)
        min_l = min(min_l, s_l)
    s_h = min_h = sum(abs(A[j] - h) for j in range(K))
    for j in range(K, N):
        s_h = s_h - abs(A[j - K] - h) + abs(A[j] - h)
        min_h = min(min_h, s_h)

    if min_l < min_h:
        hi = h - 1
        ans = min(ans, min_l)
    else:
        lo = l + 1
        ans = min(ans, min_h)
print(ans)