N, K, *A = map(int, open(0).read().split())

B = [1] * K + [-1] * (N - K)
t = 0
x = A[0]
for i in range(N):
    t += B[i] * abs(x - A[i])

B = [-1] * K + [1] * (N - K)
u = 0
x = A[-1]
for i in range(N):
    t += B[i] * abs(x - A[i])

print(min(t, u))