#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<n;i++)
using namespace std;
typedef long long ll;
const ll inf = 4611686018427387903LL;
const int MOD=998244353;
int main(){
    int N,K;
    cin >> N >> K;
    vector<ll> a(N);
    rep(i, N) cin >> a[i];
    
    int l = 0;
    int r = K - 1;
    //[l, r] を +1 にする
    
    ll ans = inf;
    ll now = 0;
    rep(i,N){
        if(l <= i && i <= r) now += abs(a[0] - a[i]);
        else now -= abs(a[0] - a[i]);
    }


    rep(i,N){
        // x = A[i]
        while(r < i || (r + 1 < N && abs(a[l] - a[i]) > abs(a[r + 1] - a[i]))){
            // 得をするので動かす
            now = now - 2 * abs(a[l] - a[i]) + 2 * abs(a[r + 1] - a[i]);
            l++;
            r++;
        }

        ans = min(ans, now);

        // i を一つ進める
        // [0, l-1]、[i+1, r]ではxを足して戻す
        // それ以外引いて戻す
        now -= (i - l + 1 + N - 1 - r - (l + (r - i))) * a[i];
        if(i + 1 < N){
            //次のx
            now -= (i + 1 - l + 1 + N - 1 - r - (l + (r - (i + 1)))) * a[i + 1];
            // now -= (i - l + 1 + N - 1 - r - (l + (r - i))) * a[i + 1];
            // now += (i - l + 1 + N - r - (l + (r - i - 1))) * a[i + 1];
            now += -2 * a[i + 1];
        }
    }

    cout << ans << endl;

    return 0;
}