#include <iostream>
#include <stdio.h>
#include <string>
#include <vector>
#include <set>
#include <cmath>
#include <algorithm>
#include <cstdio>
#include <queue>
#include <map>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int,int> pint;
typedef pair<double,int> pdi;
#define REP(i,n) for(ll i=0, i##_len=(n); i<i##_len; ++i)
#define REPR(i, n) for(ll i = n;i >= 0;i--)
#define FOR(i, m, n) for(ll i = m;i < n;i++)

int N,K;
vector<int> aa;

ll f(ll m){
  ll tmp=0,ans;
  REP(i,K){tmp += abs(aa[i]-m);}
  ans = tmp;
  int l = 0;
  for (int r = K; r < N; r++) {
    tmp += abs(aa[r]-m);
    tmp -= abs(aa[l]-m);
    ans = min(tmp,ans);
    l ++;
  }
  return ans;
}


int main(void) {
  cin >> N >> K;
  int a;
  REP(i,N){
    cin >> a;
    aa.push_back(a);
  }

  f(3);


  ll x0,x1,x2,x3;
  x0 = 0;
  x3 = pow(10,9)+10;
  x1 = (x0*2+x3)/3;
  x2 = (x0+x3*2)/3;
  ll y0,y1,y2,y3;
  for (int i = 0; i < 55; i++) {
    y1 = f(x1);
    y2 = f(x2);
    if(y1>y2){
      x0 = x1;
    }else{
      x3 = x2;
    }
    x1 = (x0*2+x3)/3;
    x2 = (x0+x3*2)/3;
  }
  cout << min(min(f(x0),y1),min(y2,f(x3))) << endl;

}