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

s = (0,N-K)
for i in s:
    first = (N-K-i) - i - K
    last = (N-K-i) - i + K - 2

    if first>=0:
        mid = i
    elif last<=0:
        mid = i + K -1
    else:
        mid = K + 2*i - ((N+1)//2)

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

    res = min(res,tmp)

print(res)