#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using vl = vector<ll>;
template<class T> using vc = vector<T>;
template<class T> using vvc = vector<vector<T>>;

#define eb emplace_back
#define all(x) (x).begin(), (x).end()
#define rep(i, n) for (ll i = 0; i < (n); i++)
#define repr(i, n) for (ll i = (n)-1; i >= 0; i--)
#define repe(i, l, r) for (ll i = (l); i < (r); i++)
#define reper(i, l, r) for (ll i = (r)-1; i >= (l); i--)
#define repa(i,n) for (auto& i: n)

template<class T1, class T2> inline bool chmax(T1 &a, const T2 &b) {if (a<b) { a=b; return 1;} return 0;}
template<class T1, class T2> inline bool chmin(T1 &a, const T2 &b) {if (b<a) { a=b; return 1;} return 0;}
struct init{init(){cin.tie(0);ios::sync_with_stdio(false);cout<<fixed<<setprecision(15);}}init_;

#ifdef DEBUG
template <class T> void verr(const set<T> &st) { repa(a, st) cerr << a << " "; cerr << endl; }
template <class S, class T> void verr(const map<S, T> &mp) { repa(a, mp) cerr << "{" << a.first << ", " << a.second << "} "; cerr << endl; }
template <class S, class T, class N> void verr(const vector<pair<S,T>>& a, const N& n) { rep(i, n) cerr << "{" << a[i].first << ", " << a[i].second << "} "; cerr << endl; }
template <class T, class N> void verr(const vector<T>& a, const N& n) { rep(i, n) cerr << a[i] << " "; cerr << endl; }
ll dbgt = 1; void err() { cerr << "passed " << dbgt++ << endl; }
template<class H, class... T> void err(H&& h,T&&... t){ cerr<< h << (sizeof...(t)?" ":"\n") << flush; if(sizeof...(t)>0) err(forward<T>(t)...); }
#endif

const ll INF = 4e18;
const ld EPS = 1e-11;
const ld PI = acos(-1.0L);
const ll MOD = 1e9 + 7;
// const ll MOD = 998244353;
//--------------------------------------------------------------------------------//

int main() {
    ll N, K;
    cin >> N >> K;
    vl A(N);
    rep(i, N) cin >> A[i];

    ll ans = 0;
    vl acc(N + 1);
    rep(i, N) acc[i + 1] = acc[i] + A[i];

    rep(i, N){
        ans += (i < K ? abs(A[i] - A[0]) : -abs(A[i] - A[0]));
    }

    ll d = 0, res = ans;
    rep(i, N - K){
        ll v1 = -2 * abs(A[i] - A[i + d]) + 2 * abs(A[i + K] - A[i + d]);
        ll sa = (N - K - i + d + 1 - (K - d - 1) - i) * ( d < K - 1 ? (A[i + d + 1] - A[i + d]) : 0);
        while(d < K - 1 and v1 > -2 * abs(A[i] - A[i + d + 1]) + 2 * abs(A[i + K] - A[i + d + 1]) + sa){
            d++;
            ans += sa;
            sa = (N - K - i + d + 1 - (K - d - 1) - i) * (d < K - 1 ? (A[i + d + 1] - A[i + d]) : 0);
            v1 = -2 * abs(A[i] - A[i + d]) + 2 * abs(A[i + K] - A[i + d]);
        }
        ans += v1;
        chmin(res, ans);
    }

    cout << res << endl;
}