from collections import defaultdict

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

ans = 1e15
for i in range(N - K + 1):
    lo, hi = 1, 10**9
    while lo <= hi:
        l = (2*lo + hi)//3
        h = (lo + 2*hi)//3
        #print(i, lo, hi)
        s_l = sum(abs(A[j] - l) for j in range(i, i + K))
        s_h = sum(abs(A[j] - h) for j in range(i, i + K))
        if s_l < s_h:
            hi = h - 1
            ans = min(ans, s_l)
        else:
            lo = l + 1
            ans = min(ans, s_h)
print(ans)