#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];
  /*if(K==0){
    ll s1 = 0,s2=0;
    rep(i,N){
      s1+=abs(a[i]-a[0]);
      s2+=abs(a[i]-a[N-1]);
    }
    cout << min(-s1,-s2) << endl;
    return 0;
  }*/
  vector<ll>imos(N+1);
  imos[0]=0;
  rep(i,N)imos[i+1]=imos[i]+a[i];
  ll ans = inf;

  for(int L=0;L+K-1<N;L++){
    int R = L + K;
    // [L, R) を + にする

    int minus = L, plus = (N-R);
    int idx;
    if(plus-minus+K-1<=0)idx = R-1;
    else if(plus-minus-(K-1)>=0)idx=L;
    else idx = L + abs(plus-minus-(K-1))/2;

    ll sum = 0, X = a[idx];
    //[0, L)について
    sum+= -L*X + imos[L];
    //[L, idx+1)について
    sum+= (idx+1-L)*X - (imos[idx+1]-imos[L]);
    //[idx+1, R)について
    sum+= -(K-(idx+1-L))*X + (imos[R]-imos[idx+1]);
    //[R, N)について
    sum+= (N-R)*X - (imos[N]-imos[R]);

    ans=min(ans,sum);
  }
  cout << ans << endl;
  return 0;
}