#include <iostream>
#include <algorithm>
#include <iomanip>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <numeric>
#include <functional>
#include <cassert>

#define debug_value(x) cerr << "line" << __LINE__ << ":<" << __func__ << ">:" << #x << "=" << x << endl;
#define debug(x) cerr << "line" << __LINE__ << ":<" << __func__ << ">:" << x << endl;

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

using namespace std;
typedef long long ll;
const ll INF = 1e18;

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << setprecision(10) << fixed;
    int n, k; cin >> n >> k;
    vector<ll> a(n);
    vector<ll> cumsum_a(n+1);
    for(int i = 0; i < n; i++){
        cin >> a[i];
        cumsum_a[i+1] = cumsum_a[i]+a[i];
    }
    // a[l]+...+a[r-1]
    auto range_sum = [&](int l, int r){
        return cumsum_a[r]-cumsum_a[l];
    };
    ll ans = INF;
    int l = 0, r = k;
    for(int c = 0; c < n; c++){
        while(r < n && a[c]-a[l] > a[r]-a[c]){
            l++; r++;
        }
        ll tmp = -(a[c]*l-range_sum(0, l));
        tmp -= range_sum(r, n)-a[c]*(n-r);
        tmp += a[c]*(c-l)-range_sum(l, c);
        tmp += range_sum(c, r)-a[c]*(r-c);
        chmin(ans, tmp);
    }
    cout << ans << endl;
}