package contest180928;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.InputMismatchException;
import java.util.Random;

public class E {
	InputStream is;
	PrintWriter out;
	String INPUT = "";
	
	void solve()
	{
		int n = ni(), K = ni();
		int[] a = na(n);
		Node root = null;
		Node[] nodes = new Node[n];
		long ans = Long.MAX_VALUE;
		for(int i = 0;i < n;i++) {
			nodes[i] = new Node(a[i], a[i]);
			root = insertb(root, nodes[i]);
			if(i-K >= 0) {
				root = erase(root, index(nodes[i-K]));
			}
			if(i-(K-1) >= 0) {
				assert count(root) == K;
				long L = sum(root, 0, count(root)/2);
				long M = get(root, count(root)/2).v;
				long R = sum(root, count(root)/2, count(root));
				ans = Math.min(ans, M*(count(root)/2)-L + (R-M*(count(root)-count(root)/2)));
			}
		}
		out.println(ans);
	}
	
	public static Random gen = new Random();
	
	static public class Node
	{
		public int id;
		public long v; // value
		public long priority;
		public Node left, right, parent;
		
		public int count;
		
		public long sum;
		
		public Node(int id, int v)
		{
			this.id = id;
			this.v = v;
			priority = gen.nextLong();
			update(this);
		}
		
		@Override
		public String toString() {
			StringBuilder builder = new StringBuilder();
			builder.append("Node [v=");
			builder.append(v);
			builder.append(", count=");
			builder.append(count);
			builder.append(", parent=");
			builder.append(parent != null ? parent.v : "null");
			builder.append(", sum=");
			builder.append(sum);
			builder.append("]");
			return builder.toString();
		}
	}

	public static Node update(Node a)
	{
		if(a == null)return null;
		a.count = 1;
		if(a.left != null)a.count += a.left.count;
		if(a.right != null)a.count += a.right.count;
		
		a.sum = a.v;
		if(a.left != null)a.sum += a.left.sum;
		if(a.right != null)a.sum += a.right.sum;
		return a;
	}
	
	public static Node disconnect(Node a)
	{
		if(a == null)return null;
		a.left = a.right = a.parent = null;
		return update(a);
	}
	
	public static Node root(Node x)
	{
		if(x == null)return null;
		while(x.parent != null)x = x.parent;
		return x;
	}
	
	public static int count(Node a)
	{
		return a == null ? 0 : a.count;
	}
	
	public static void setParent(Node a, Node par)
	{
		if(a != null)a.parent = par;
	}
	
	public static long sum(Node a, int L, int R)
	{
		if(a == null || L >= R || L >= count(a) || R <= 0)return 0L;
		if(L <= 0 && R >= count(a)){
			return a.sum;
		}else{
			long ret = 0;
			ret += sum(a.left, L, R);
			ret += sum(a.right, L-count(a.left)-1, R-count(a.left)-1);
			if(L <= count(a.left) && count(a.left) < R)ret += a.v;
			return ret;
		}
	}
	
	public static Node merge(Node a, Node b)
	{
		if(b == null)return a;
		if(a == null)return b;
		if(a.priority > b.priority){
			setParent(a.right, null);
			setParent(b, null);
			a.right = merge(a.right, b);
			setParent(a.right, a);
			return update(a);
		}else{
			setParent(a, null);
			setParent(b.left, null);
			b.left = merge(a, b.left);
			setParent(b.left, b);
			return update(b);
		}
	}
	
	// [0,K),[K,N)
	public static Node[] split(Node a, int K)
	{
		if(a == null)return new Node[]{null, null};
		if(K <= count(a.left)){
			setParent(a.left, null);
			Node[] s = split(a.left, K);
			a.left = s[1];
			setParent(a.left, a);
			s[1] = update(a);
			return s;
		}else{
			setParent(a.right, null);
			Node[] s = split(a.right, K-count(a.left)-1);
			a.right = s[0];
			setParent(a.right, a);
			s[0] = update(a);
			return s;
		}
	}
	
	public static Node insert(Node a, int K, Node b)
	{
		if(a == null)return b;
		if(b.priority < a.priority){
			if(K <= count(a.left)){
				a.left = insert(a.left, K, b);
				setParent(a.left, a);
			}else{
				a.right = insert(a.right, K-count(a.left)-1, b);
				setParent(a.right, a);
			}
			return update(a);
		}else{
			Node[] ch = split(a, K);
			b.left = ch[0]; b.right = ch[1];
			setParent(b.left, b);
			setParent(b.right, b);
			return update(b);
		}
	}
	
	public static Node insertb(Node root, Node x)
	{
		int ind = search(root, x.id);
		if(ind < 0){
			// insert
			ind = -ind-1;
			return insert(root, ind, x);
		}else{
			return insert(root, ind, x);
//			// add
//			return insert(root, ind, x);
//			Node t = get(root, ind);
//			t.v += x.v;
//			while(t != null){
//				update(t);
//				t = t.parent;
//			}
//			return root;
		}
	}
	
	// delete K-th
	public static Node erase(Node a, int K)
	{
		if(a == null)return null;
		if(K < count(a.left)){
			a.left = erase(a.left, K);
			setParent(a.left, a);
			return update(a);
		}else if(K == count(a.left)){
			setParent(a.left, null);
			setParent(a.right, null);
			Node aa = merge(a.left, a.right);
			disconnect(a);
			return aa;
		}else{
			a.right = erase(a.right, K-count(a.left)-1);
			setParent(a.right, a);
			return update(a);
		}
	}
	
	public static Node get(Node a, int K)
	{
		while(a != null){
			if(K < count(a.left)){
				a = a.left;
			}else if(K == count(a.left)){
				break;
			}else{
				K = K - count(a.left)-1;
				a = a.right;
			}
		}
		return a;
	}
	
	public static int lowerBound(Node a, int q)
	{
		int lcount = 0;
		while(a != null){
			if(a.v >= q){
				a = a.left;
			}else{
				lcount += count(a.left) + 1;
				a = a.right;
			}
		}
		return lcount;
	}
	
	public static int search(Node a, int q)
	{
		int lcount = 0;
		while(a != null){
			if(a.id == q){
				lcount += count(a.left);
				break;
			}
			if(q < a.id){
				a = a.left;
			}else{
				lcount += count(a.left) + 1;
				a = a.right;
			}
		}
		return a == null ? -(lcount+1) : lcount;
	}
	
	public static int index(Node a)
	{
		if(a == null)return -1;
		int ind = count(a.left);
		while(a != null){
			Node par = a.parent;
			if(par != null && par.right == a){
				ind += count(par.left) + 1;
			}
			a = par;
		}
		return ind;
	}
	
	public static Node[] nodes(Node a) { return nodes(a, new Node[count(a)], 0, count(a)); }
	public static Node[] nodes(Node a, Node[] ns, int L, int R)
	{
		if(a == null)return ns;
		nodes(a.left, ns, L, L+count(a.left));
		ns[L+count(a.left)] = a;
		nodes(a.right, ns, R-count(a.right), R);
		return ns;
	}
	
	public static String toString(Node a, String indent)
	{
		if(a == null)return "";
		StringBuilder sb = new StringBuilder();
		sb.append(toString(a.left, indent + "  "));
		sb.append(indent).append(a).append("\n");
		sb.append(toString(a.right, indent + "  "));
		return sb.toString();
	}

	
	void run() throws Exception
	{
		is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes());
		out = new PrintWriter(System.out);
		
		long s = System.currentTimeMillis();
		solve();
		out.flush();
		if(!INPUT.isEmpty())tr(System.currentTimeMillis()-s+"ms");
//		Thread t = new Thread(null, null, "~", Runtime.getRuntime().maxMemory()){
//			@Override
//			public void run() {
//				long s = System.currentTimeMillis();
//				solve();
//				out.flush();
//				if(!INPUT.isEmpty())tr(System.currentTimeMillis()-s+"ms");
//			}
//		};
//		t.start();
//		t.join();
	}
	
	public static void main(String[] args) throws Exception { new E().run(); }
	
	private byte[] inbuf = new byte[1024];
	public int lenbuf = 0, ptrbuf = 0;
	
	private int readByte()
	{
		if(lenbuf == -1)throw new InputMismatchException();
		if(ptrbuf >= lenbuf){
			ptrbuf = 0;
			try { lenbuf = is.read(inbuf); } catch (IOException e) { throw new InputMismatchException(); }
			if(lenbuf <= 0)return -1;
		}
		return inbuf[ptrbuf++];
	}
	
	private boolean isSpaceChar(int c) { return !(c >= 33 && c <= 126); }
	private int skip() { int b; while((b = readByte()) != -1 && isSpaceChar(b)); return b; }
	
	private double nd() { return Double.parseDouble(ns()); }
	private char nc() { return (char)skip(); }
	
	private String ns()
	{
		int b = skip();
		StringBuilder sb = new StringBuilder();
		while(!(isSpaceChar(b))){ // when nextLine, (isSpaceChar(b) && b != ' ')
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}
	
	private char[] ns(int n)
	{
		char[] buf = new char[n];
		int b = skip(), p = 0;
		while(p < n && !(isSpaceChar(b))){
			buf[p++] = (char)b;
			b = readByte();
		}
		return n == p ? buf : Arrays.copyOf(buf, p);
	}
	
	private int[] na(int n)
	{
		int[] a = new int[n];
		for(int i = 0;i < n;i++)a[i] = ni();
		return a;
	}
	
	private long[] nal(int n)
	{
		long[] a = new long[n];
		for(int i = 0;i < n;i++)a[i] = nl();
		return a;
	}
	
	private char[][] nm(int n, int m) {
		char[][] map = new char[n][];
		for(int i = 0;i < n;i++)map[i] = ns(m);
		return map;
	}
	
	private int[][] nmi(int n, int m) {
		int[][] map = new int[n][];
		for(int i = 0;i < n;i++)map[i] = na(m);
		return map;
	}
	
	private int ni() { return (int)nl(); }
	
	private long nl()
	{
		long num = 0;
		int b;
		boolean minus = false;
		while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'));
		if(b == '-'){
			minus = true;
			b = readByte();
		}
		
		while(true){
			if(b >= '0' && b <= '9'){
				num = num * 10 + (b - '0');
			}else{
				return minus ? -num : num;
			}
			b = readByte();
		}
	}
	
	private static void tr(Object... o) { System.out.println(Arrays.deepToString(o)); }
}