#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <cmath>
using namespace std;
using ll = long long;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);

    int n, k;
    cin >> n >> k;

    vector<int> a(n);
    for (int i = 0; i < n; i++) {
        cin >> a[i];
    }

    vector<ll> s(n + 1, 0);
    for (int i = 0; i < n; i++) {
        s[i + 1] = s[i] + a[i];
    }

    ll r = 1LL << 60;
    int l = 0;
    for (int i = 0; i < n; i++) {
        ll x = a[i];
        while (l + k < n && abs(x - a[l]) > abs(x - a[l + k])) l++;
        ll t = 0;
        if (l < i) t += -(s[min(i, l + k)] - s[l]) + x * (min(i, l + k) - l);
        if (l + k > i) t += (s[l + k] - s[max(i, l)]) - x * (l + k - max(i, l));
        t *= 2;
        t -= (s[n] - s[i]) - x * (n - i) - (s[i] - s[0]) + x * i;
        r = min(r, t);
    }

    cout << r << endl;

    return 0;
}