/* -*- coding: utf-8 -*-
 *
 * 1391.cc:  No.1391 ±1 Abs Sum - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 200000;
const long long LINF = 1LL << 62;

/* typedef */

typedef long long ll;

/* global variables */

int as[MAX_N];
ll ass[MAX_N + 1];

/* subroutines */

/* main */

int main() {
  int n, k;
  scanf("%d%d", &n, &k);

  for (int i = 0; i < n; i++)
    scanf("%d", as + i), ass[i + 1] = ass[i] + as[i];

  ll minsum = LINF;
  for (int i = 0, j0 = 0, j1 = k; i < n; i++) {
    while (j1 < n && as[j1] - as[i] < as[i] - as[j0]) j0++, j1++;

    ll sum =
      - ((ll)as[i] * j0 - ass[j0])
      + ((ll)as[i] * (i - j0) - (ass[i] - ass[j0]))
      + ((ass[j1] - ass[i]) - (ll)as[i] * (j1 - i))
      - ((ass[n] - ass[j1]) - (ll)as[i] * (n - j1));

    if (minsum > sum) {
      minsum = sum;
      //printf("i=%d,j0=%d,j1=%d -> sum=%lld\n", i, j0, j1, sum);
    }
  }

  printf("%lld\n", minsum);
  return 0;
}