Problem: You have a playlist consisting of n songs. The i-th song is characterized by two numbers t_i and b_i — its length and beauty respectively. The pleasure of listening to set of songs is equal to the total length of the songs in the set multiplied by the minimum beauty among them. For example, the pleasure of listening to a set of 3 songs having lengths [5, 7, 4] and beauty values [11, 14, 6] is equal to (5 + 7 + 4) ⋅ 6 = 96.

You need to choose at most k songs from your playlist, so the pleasure of listening to the set of these songs them is maximum possible.

Input

The first line contains two integers n and k (1 ≤ k ≤ n ≤ 3 ⋅ 10^5) – the number of songs in the playlist and the maximum number of songs you can choose, respectively.

Each of the next n lines contains two integers t_i and b_i (1 ≤ t_i, b_i ≤ 10^6) — the length and beauty of i-th song.

Output

Print one integer — the maximum pleasure you can get.

Examples

Input


4 3
4 7
15 1
3 6
6 8


Output


78


Input


5 3
12 31
112 4
100 100
13 55
55 50


Output


10000

Note

In the first test case we can choose songs {1, 3, 4}, so the total pleasure is (4 + 3 + 6) ⋅ 6 = 78.

In the second test case we can choose song 3. The total pleasure will be equal to 100 ⋅ 100 = 10000.

Solution (in JAVA):

Solution:



import java.io.BufferedReader;


import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.StringTokenizer;
import java.util.TreeSet;



public class C implements Runnable
{

	static BufferedReader br = null;
	static PrintWriter pw = null;
	static StringTokenizer stk = new StringTokenizer("");

	public static void main(String[] args)
	{
		try
		{
			//br = new BufferedReader(new FileReader("input.txt"));
			//pw = new PrintWriter("output.txt");
			br = new BufferedReader(new InputStreamReader(System.in));
			pw = new PrintWriter(new OutputStreamWriter(System.out));
			
		} catch (Exception e)
		{
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		(new Thread(new C())).start();
	}

	public void nline()
	{
		try
		{
			stk = new StringTokenizer(br.readLine());
		} catch (IOException e)
		{
			e.printStackTrace();
		}
	}

	public int ni()
	{
		while (!stk.hasMoreTokens())
			nline();
		return Integer.valueOf(stk.nextToken());
	}

	public double nd()
	{
		while (!stk.hasMoreTokens())
			nline();
		return Double.valueOf(stk.nextToken());
	}

	public String nwrd()
	{
		while (!stk.hasMoreTokens())
			nline();
		return stk.nextToken();
	}

	public long nl()
	{
		while (!stk.hasMoreTokens())
			nline();
		return Long.valueOf(stk.nextToken());
	}

	public BigInteger nbi()
	{
		while (!stk.hasMoreTokens())
			nline();
		return new BigInteger(stk.nextToken());
	}

	public char nc()
	{
		while (!stk.hasMoreTokens())
			nline();
		return stk.nextToken().charAt(0);
	}

	public boolean isready()
	{
		try
		{
			return br.ready();
		} catch (IOException e)
		{
			return false;
		}
	}

	String rline()
	{
		try
		{
			return br.readLine();
		} catch (IOException e)
		{
			e.printStackTrace();
		}
		return null;
	}

	public void run()
	{
		solve();
		pw.close();
	}
	public class Hero {
		public long max_health;
		public long regen;
		public Hero(long h, long regen) {
			// TODO Auto-generated constructor stub
			max_health = h;
			this.regen = regen;
		}
	}
	public class Pair implements Comparable<Pair>{
		public int a;
		public int b;
		public Pair( int a , int b) {
			// TODO Auto-generated constructor stub
			this.a = a;
			this.b = b;
		}
		@Override
		public int compareTo(Pair o) {
			// TODO Auto-generated method stub
			if	( o.b - b == 0)
				return (int) (a - o.a);
			return (int) (o.b - b);

		}
		public  String toString() {
			return a + " " + b;
		}
		
	}
	
	
	

	public void solve()
	{
		int	n = ni();
		int k = ni();
		ArrayList<Pair> pairs = new ArrayList<>(n);
		for( int i =0; i < n; i++ )
			pairs.add(new Pair(ni(), ni()));
		Collections.sort(pairs);
		TreeSet<Pair> bestLens = new TreeSet<>( new Comparator<Pair>() {

			@Override
			public int compare(Pair o1, Pair o2) {
				// TODO Auto-generated method stub
				if	( o1.a - o2.a == 0)
					return (int) (o1.b - o2.b);
				return (int) (o1.a - o2.a);
			}
		});
		long allLenBest = 0;
		long res = 0;
		for(int i =0; i<n; i++)
		{
			Pair curPair = pairs.get(i);
			if (bestLens.size() == k) {
				if (bestLens.first().a >= curPair.a)
					continue;
				else
				{
					allLenBest -= bestLens.pollFirst().a;
				}
			}
			bestLens.add(new Pair((int) curPair.a , i));
			allLenBest += curPair.a;
			
			if(res < allLenBest * curPair.b )
				res = allLenBest * curPair.b;
			
		}
		pw.println(res);
		
		
				
	}

}