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:
        mi = (lo + hi + 1)//2
        #print(i, lo, hi)
        t_lo = sum(abs(A[j] - lo) for j in range(i, i + K))
        t_hi = sum(abs(A[j] - hi) for j in range(i, i + K))
        if t_lo < t_hi:
            hi = mi - 1
            ans = min(ans, t_lo)
        else:
            lo = mi + 1
            ans = min(ans, t_hi)
print(ans)