#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); i++)
#define repi(i, a, b) for (int i = (a); i < (b); i++)
#define all(a) (a).begin(), (a).end()

using namespace std;
using i32 = int;
using i64 = long long;
using f64 = double;
using f80 = long double;
using vi32 = vector<i32>;
using vvi32 = vector<vi32>;
using vi64 = vector<i64>;
using vvi64 = vector<vi64>;
using vstr = vector<string>;

template <typename T> inline bool amax(T &x, T y) { if (x < y) { x = y; return true; } return false; }
template <typename T> inline bool amin(T &x, T y) { if (y < x) { x = y; return true; } return false; }

random_device rng;

template <class Val>
struct Treap {
  struct Node {
    Val v;
    int priority;
    Node *lef, *rig;
    int size_;
    Val sum;
    
    Node(Val v) : v(v), priority(rng()), lef(nullptr), rig(nullptr), size_(1), sum(v) {}
    
    int size() const { return size_; }

    static Node* update(Node* a) {
      if (a == nullptr) return nullptr;
      a->size_ = 1 + size(a->lef) + size(a->rig);
      a->sum = a->v;
      if (a->lef != nullptr) a->sum = a->sum + a->lef->sum;
      if (a->rig != nullptr) a->sum = a->sum + a->rig->sum;
      return a;
    }

    static int size(const Node* x) { return x == nullptr ? 0 : x->size_; }

    static Node* merge(Node* a, Node* b) {
      if (a == nullptr) return b;
      if (b == nullptr) return a;
      if (a->priority > b->priority) {
        a->rig = merge(a->rig, b);
        return update(a);
      } else {
        b->lef = merge(a, b->lef);
        return update(b);
      }
    }

    static pair<Node*, Node*> split(Node* a, int k) {
      if (a == nullptr) return make_pair(nullptr, nullptr);
      if (k <= size(a->lef)) {
        auto s = split(a->lef, k);
        a->lef = s.second;
        s.second = update(a);
        return s;
      } else {
        auto s = split(a->rig, k - size(a->lef) - 1);
        a->rig = s.first;
        s.first = update(a);
        return s;
      }
    }
  };

  using np = Node*;

  static pair<np, np> split_less(np a, Val v) {
    if (a == nullptr) return make_pair(nullptr, nullptr);
    if (a->v < v) {
      auto s = split_less(a->rig, v);
      a->rig = s.first;
      s.first = Node::update(a);
      return s;
    } else {
      auto s = split_less(a->lef, v);
      a->lef = s.second;
      s.second = Node::update(a);
      return s;
    }
  }

  static np insert_b(np a, np v) {
    auto lr = split_less(a, v->v);
    return Node::merge(Node::merge(lr.first, v), lr.second);
  }
  
  static np erase_b(np a, Val v) {
    auto lr = split_less(a, v);
    auto mr = Node::split(lr.second, 1);
    return Node::merge(lr.first, mr.second);
  }

  static np get_k(np a, int k) {
    while (a != nullptr) {
      if (k < Node::size(a->lef)) {
        a = a->lef;
      } else if (k == Node::size(a->lef)) {
        break;
      } else {
        k = k - Node::size(a->lef) - 1;
        a = a->rig;
      }
    }
    return a;
  }

public:
  np root;

  Treap() : root(nullptr) {}
  Treap(np root) : root(root) {}
  Treap(Treap l, Treap r) : root(Node::merge(l.root, r.root)) {}

  int size() const { return Node::size(root); }

  pair<Treap, Treap> split_k(int k) {
    auto lr = Node::split(root, k);
    return make_pair(Treap(lr.first), Treap(lr.second));
  }

  Val operator[](int k) const {
    assert(size() > k);
    return get_k(root, k)->v;
  }

  void insert_b(const Val val) {
    root = insert_b(root, new Node(val));
  }

  void erase_b(const Val val) {
    if (contains_b(val)) root = erase_b(root, val);
  }

  bool contains_b(const Val q) const {
    auto a = root;
    while (a != nullptr) {
      if (a->v == q) return true;
      else if (a->v < q) a = a->rig;
      else a = a->lef;
    }
    return false;
  }
};

i64 solve(const int n, const int k, const vi32 &A) {
  if (k == 1) return 0;

  int l = (k + 1) / 2;
  int m = k - l;
  Treap<i64> treap;

  i64 ans = 1e18;

  rep(i, n) {
    treap.insert_b(A[i]);
    if (i >= k) treap.erase_b(A[i - k]);
    if (i >= k - 1) {
      i64 mid = treap[l - 1];
      
      auto splited = treap.split_k(l);
      
      i64 sum_of_lower = splited.first.root->sum;
      i64 sum_of_higher = splited.second.root->sum;
      
      treap = Treap<i64>(splited.first, splited.second);

      i64 inc_cost = mid * l - sum_of_lower;
      i64 dec_cost = sum_of_higher - mid * m;
      i64 cand = inc_cost + dec_cost;

      amin(ans, cand);
    }
  }

  return ans;
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout << fixed << setprecision(16);
  int n, k;
  cin >> n >> k;
  vi32 A(n);
  rep(i, n) cin >> A[i];
  cout << solve(n, k, A) << endl;
  return 0;
}