#include "bits/stdc++.h"
using namespace std;

using ll = long long;
using P = pair<ll, ll>;
const ll INF = (1LL << 61);
ll mod = 998244353;



signed main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	ll N, K; cin >> N >> K;
	vector<ll>A(N); for (int i = 0; i < N; i++)cin >> A[i];
	vector<ll>sum(N + 1);
	for (int i = 0; i < N; i++)sum[i + 1] = sum[i] + A[i];
	ll ans = INF;
	ll l = 0, r = K;
	for (int i = 0; i < N; i++) {
		if (i == r)l++, r++;
		while (r < N && abs(A[i] - A[l]) > abs(A[i] - A[r]))l++, r++;
		ll now = A[i] * (i - l) - (sum[i] - sum[l]) + (sum[r] - sum[i]) - A[i] * (r - i);
		now -= (sum[N] - sum[r]) - A[i] * (N - r) + A[i] * l - sum[l];
		ans = min(ans, now);
	}
	cout << ans << endl;
	return 0;
}