/* -*- coding: utf-8 -*-
 *
 * 738.cc:  No.738 平らな農地 - 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 = 100000;
const long long LINF = 1LL << 60;

/* typedef */

typedef long long ll;
typedef pair<ll,ll> pll;

template <typename T, const int BUFSIZE>
struct TreapSum {
  struct Node {
    T key, minkey, sum;
    int fix, size;
    Node *left, *right;

    void print(int k) {
      printf("%d: key=%lld, minkey=%lld, sum=%lld, fix=%d, size=%d\n",
	     k, (ll)key, (ll)minkey, (ll)sum, fix, size);
    }
    void print() { print(0); }
  };
  typedef Node *node;
  typedef pair<T,T> ptt;

  node root, nullnode, buf;
  Node buf0[BUFSIZE], buf1;

  const T TINF;
  
  TreapSum(T _TINF): TINF(_TINF) {
    nullnode = &buf1;
    nullnode->left = nullnode->right = nullnode;
    nullnode->key = nullnode->minkey = TINF;
    nullnode->sum = 0;
    nullnode->fix = nullnode->size = 0;
    clear();
    srand(time(NULL));
  }

  void clear() { buf = buf0; root = nullnode; }
  int size() { return root->size; }
  T sum() { return root->sum; }

  void update(node& t) {
    t->size = 1 + t->left->size + t->right->size;
    t->minkey = t->key;
    if (t->minkey > t->left->minkey) t->minkey = t->left->minkey;
    if (t->minkey > t->right->minkey) t->minkey = t->right->minkey;
    t->sum = t->key + t->left->sum + t->right->sum;
  }

  node gen_node(T x) {
    node t = buf++;
    t->left = t->right = nullnode;
    t->key = t->minkey = t->sum = x;
    t->fix = rand();
    t->size = 1;
    return t;
  }
  
  void rot_l(node& k1) {
    node k2 = k1->right;
    k1->right = k2->left;
    k2->left = k1;
    update(k1);
    update(k2);
    k1 = k2;
  }

  void rot_r(node& k1) {
    node k2 = k1->left;
    k1->left = k2->right;
    k2->right = k1;
    update(k1);
    update(k2);
    k1 = k2;
  }

  void insert(node& t, T x) {
    if (t == nullnode)
      t = gen_node(x);
    else {
      //if (t->key == x) return;
      if (x < t->key) {
	insert(t->left, x);
	update(t);
	if (t->left->fix > t->fix) rot_r(t);
      }
      else {
	insert(t->right, x);
	update(t);
	if (t->right->fix > t->fix) rot_l(t);
      }
    }
  }
  void insert(T x) { insert(root, x); }

  void remove_node(node& t) {
    if (t == nullnode) return;
    if (t->left == nullnode || t->right == nullnode) {
      if (t->left == nullnode)
	t = t->right;
      else
	t = t->left;
    }
    else {
      if (t->left->fix < t->right->fix) {
	rot_l(t);
	remove_node(t->left);
	update(t);
      }
      else {
	rot_r(t);
	remove_node(t->right);
	update(t);
      }
    }
  }

  void remove(node& t, T x) {
    if (t != nullnode) {
      if (t->key == x)
	remove_node(t);
      else if (x < t->key) {
	remove(t->left, x);
	update(t);
      }
      else {
	remove(t->right, x);
	update(t);
      }
    }
  }
  void remove(T x) { remove(root, x); }
  
  ptt findat(int i) {
    node t = root;
    T lsum = 0;
    while (t != nullnode) {
      int lsize = t->left->size;
      if (i == lsize) return ptt(t->key, lsum + t->left->sum);
      if (i < lsize)
	t = t->left;
      else {
	i -= lsize + 1;
	lsum += t->key + t->left->sum;
	t = t->right;
      }
    }
    return ptt(TINF, 0);
  }

  void print(node t, int k, int indent) {
    if (t == nullnode) return;
    if (t != NULL) {
      for (int i = 0; i < indent; i++) putchar(' '), putchar(' ');
      t->print(k + t->left->size);
      print(t->left, k, indent + 1);
      print(t->right, k + t->left->size + 1, indent + 1);
    }
  }
  void print() { print(root, 0, 0); }

  void inorder(node t) {
    if (t != nullnode && t != NULL) {
      inorder(t->left);
      cout << t->key << ' ';
      inorder(t->right);
    }
  }
  void inorder() {
    inorder(root);
    cout << endl;
  }
};

/* global variables */

int as[MAX_N];
TreapSum<ll,MAX_N> trp(LINF);

/* subroutines */

/* main */

int main() {
  int n, k;
  scanf("%d%d", &n, &k);
  for (int i = 0; i < n; i++) scanf("%d", &as[i]);

  if (k == 1) {
    puts("0");
    return 0;
  }
  
  for (int i = 0; i < k - 1; i++) trp.insert(as[i]);

  int hk = (k - 1) / 2;
  ll mind = LINF;

  for (int i = 0, j = k - 1; j < n; i++, j++) {
    trp.insert(as[j]);
    ll asum = trp.sum();

    for (int dk = 0; dk < 2; dk++) {
      int hk0 = hk + dk;
      pll r = trp.findat(hk0);
      ll &a0 = r.first, &lsum = r.second;
      ll d = ((asum - lsum) - a0 * (k - hk0)) - (lsum - a0 * hk0);
      if (mind > d) mind = d;
      //printf("%d-%d: hk0=%d, asum=%lld, lsum=%lld, a0=%lld, d=%lld\n",
      //i, j, hk0, asum, r.second, a0, d);
    }

    trp.remove(as[i]);
  }

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