#include <iostream>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <string>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <stdio.h>
using namespace std;
#define int long long
int MOD = 1000000007;
template<typename T>
struct AVL {
	struct node {
		T key;
		int size, height, sum;
		node *child[2];
		node(const T &key) :key(key), size(1), height(1),sum(key) {
			child[0] = child[1] = 0;
		}
	} *root;
	typedef node *pointer;
	AVL() { root = NULL; }
	pointer find(T key) {
		return find(root, key);
	}
	node *find(node *t, const T key) {
		if (t == NULL) return NULL;
		if (key == (t->key)) return t;
		else if (key < (t->key)) return find(t->child[0], key);
		else return find(t->child[1], key);
	}
	void insert(const T key) {
		root = insert(root, new node(key));
	}
	node *insert(node *t, node *x) {
		if (t == NULL) return x;
		if ((x->key) <= (t->key)) t->child[0] = insert(t->child[0], x);
		else t->child[1] = insert(t->child[1], x);
		t->size += 1;
		return balance(t);
	}
	void erase(const T key) {
		T t = key;
		if (find(t) == NULL) return;
		root = erase(root, key);
	}
	node *erase(node *t, const int x) {
		if (t == NULL) return NULL;
		if (x == (t->key)) {
			return move_down(t->child[0], t->child[1]);
		}
		else {
			if (x < (t->key)) t->child[0] = erase(t->child[0], x);
			else t->child[1] = erase(t->child[1], x);
			t->size -= 1;
			return balance(t);
		}
	}
	node *move_down(node *t, node *rhs) {
		if (t == NULL) return rhs;
		t->child[1] = move_down(t->child[1], rhs);
		return balance(t);
	}
	int sz(node *t) {
		if (t != NULL) return t->size;
		return 0;
	}
	int ht(node *t) {
		if (t != NULL) return t->height;
		return 0;
	}
	int sm(node *t) {
		if (t != NULL) return t->sum;
		return 0;
	}
	node *rotate(node *t, int l, int r) {
		node *s = t->child[r];
		t->child[r] = s->child[l];
		s->child[l] = balance(t);
		if (t != NULL) t->size = sz(t->child[0]) + sz(t->child[1]) + 1;
		if (s != NULL) s->size = sz(s->child[0]) + sz(s->child[1]) + 1;
		if (t != NULL) t->sum = sm(t->child[0]) + sm(t->child[1]) + t->key;
		if (s != NULL) s->sum = sm(s->child[0]) + sm(s->child[1]) + s->key;
		return balance(s);
	}
	node *balance(node *t) {
		for (int i = 0; i < 2; i++) {
			if (ht(t->child[!i]) - ht(t->child[i]) < -1) {
				if (ht(t->child[i]->child[!i]) - ht(t->child[i]->child[i]) > 0)
					t->child[i] = rotate(t->child[i], i, !i);
				return rotate(t, !i, i);
			}
		}
		if (t != NULL) t->height = max(ht(t->child[0]), ht(t->child[1])) + 1;
		if (t != NULL) t->size = sz(t->child[0]) + sz(t->child[1]) + 1;
		if (t != NULL) t->sum = sm(t->child[0]) + sm(t->child[1]) + t->key;
		return t;
	}
	pair<pointer, int> rank(int k) {
		return rank(root, k);
	}
	pair<pointer, int> rank(node *t, int k) {
		if (t == NULL) return make_pair((pointer)NULL, (int)0);
		int m = sz(t->child[0]);
		if (k < m) {
			pair<pointer, int> res = rank(t->child[0], k);
			return res;
		}
		if (k == m) return make_pair(t, t->key + sm(t->child[0]));
		if (k > m) {
			pair<pointer, int> res = rank(t->child[1], k - m - 1);
			res.second += t->key + sm(t->child[0]);
			return res;
		}
	}
	int index(T key) {
		if (find(key) == NULL) return -1;
		return index(root, key);
	}
	int index(node *t, T key) {
		if (key == (t->key)) return sz(t->child[0]);
		if (key < (t->key)) return index(t->child[0], key);
		else return sz(t) - sz(t->child[1]) + index(t->child[1], key);
	}
};
signed main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	int N, K;
	cin >> N >> K;
	vector<int> A(N);
	int res = (int)1 << 60;
	for (int i = 0; i < N; i++) {
		cin >> A[i];
	}
	AVL<int> avl;
	int sum = 0;
	for (int i = 0; i < K - 1; i++) {
		avl.insert(A[i]);
		sum += A[i];
	}
	int ans;
	int l = ((K + 1) / 2);
	for (int i = K - 1; i < N; i++) {
		avl.insert(A[i]);
		sum += A[i];

		auto p = avl.rank((K - 1) / 2);
		ans = p.first->key * l - p.second;
		ans += (sum - p.second) - p.first->key * (K - l);
		res = min(res, ans);
		//cerr << i << " " << p.first->key << " " << p.second << endl;
		avl.erase(A[i - K + 1]);
		sum -= A[i - K + 1];
	}

	cout << res << endl;
}