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

if not K:
    tmp1 = -sum(abs(A[i]-A[0]) for i in range(N))
    tmp2 = -sum(abs(A[i]-A[N-1]) for i in range(N))
    exit(print(min(tmp1,tmp2)))

imos = [A[i] for i in range(N)]
for i in range(1,N):
    imos[i] += imos[i-1]

res = 10**18
l = 0
for i in range(N-K+1):
    while l+K < N and A[l+K] - A[i] < A[i] - A[l]:
        l += 1

    tmp = 0
    tmp += imos[l-1] * (l > 0) - A[i] * l
    tmp += A[i] * (i - l + 1) - imos[i] + imos[l-1] * (l > 0)
    tmp += imos[l+K-1] - imos[i] - A[i] * (l + K - i - 1)
    tmp += A[i] * (N - l - K) - imos[N-1] + imos[l+K-1]

    res = min(res,tmp)

print(res)