n, k = map(int, input().split())
A = list(map(int, input().split()))
cum = [0]
for a in A:
    cum.append(cum[-1] + a)

ans = 1 << 60
r = k
for i, a in enumerate(A):
    while r < n and A[r] - A[i] < A[i] - A[r - k]:
        r += 1

    l = r - k
    tot = 0
    tot -= (cum[n] - cum[r]) - a * (n - r)
    tot += (cum[r] - cum[i]) - a * (r - i)
    tot -= (cum[i] - cum[l]) - a * (i - l)
    tot += (cum[l] - cum[0]) - a * l
    ans = min(ans, tot)

print(ans)