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.util.Scanner;
import java.util.StringTokenizer;



import java.util.*;
  
public class er110a
{
    //By shwetank_verma
	static boolean visited[][];
	static int dx[]= {-1,0,1,0};
	static int dy[]= {0,1,0,-1};
	static boolean isValid(char ch[][],int x,int y,int n,int m) {
		if(x<0||x>=n||y<0||y>=m) {
			return false;
		}
		if(ch[x][y]=='#'||visited[x][y]) {
			return false;
		}
		return true;
		
	}
	static void dfs(char ch[][],int x,int y,int n,int m) {
		visited[x][y]=true;
		for(int i=0;i<4;i++) {
			if(isValid(ch,x+dx[i],y+dy[i],n,m))
			dfs(ch,x+dx[i],y+dy[i],n,m);
		}
	}
	static class Point implements Comparable<Point>
	{
	    int x, y;
	    Point(int x, int y)
	    {
	        this.x = x;
	        this.y = y;
	    }
	    
	    public int compareTo(Point P)
	    {
	        return this.x - P.x;
	    }
	}
	public static void main(String[] args)
    {
        FastReader sc=new FastReader();
        
                int t=1;
           //    t=sc.nextInt();
                while(t-->0){
                int n=sc.nextInt();
                int k=sc.nextInt();
              //  HashMap<Point,Long> hm=new HashMap<>();
                int a[][]=new int[n][2];
                for(int i=0;i<n;i++) {
                	int x=sc.nextInt();
                	int y=sc.nextInt();
                	a[i][0]=x;
                	a[i][1]=y;
                	
                }
                Arrays.sort(a, (aa, bb) -> Integer.compare(aa[1], bb[1]));
                //TreeSet<Point> ts=new TreeSet<>();
                PriorityQueue<Integer> pq=new PriorityQueue<>();
                long ans=0;
                long max=0;
                int cnt=0;
                for(int i=n-1;i>=0;i--) {
                	//ts.add(new Point(a[i][1],i));
                	ans+=a[i][0];
                	cnt++;
                	if(cnt>k) {
                		ans-=pq.poll();
                		
                	}
                	max=Math.max(max,1L*ans*(long)a[i][1]);
                	pq.add(a[i][0]);
                	
                }
                System.out.println(max);
                }
           
         
    }

static void ruffleSort(long[] a) {
		int n=a.length;
		Random r=new Random();
		for (int i=0; i<a.length; i++) {
			long oi=r.nextInt(n), temp=a[i];
			a[i]=a[(int)oi];
			a[(int)oi]=temp;
		}
		Arrays.sort(a);
	}
static void ruffleSort(int[] a) {
		int n=a.length;
		Random r=new Random();
		for (int i=0; i<a.length; i++) {
			int oi=r.nextInt(n), temp=a[i];
			a[i]=a[oi];
			a[oi]=temp;
		}
		Arrays.sort(a);
	}

    static class FastReader
    {
        BufferedReader br;
        StringTokenizer st;
  
        public FastReader()
        {
            br = new BufferedReader(new
                     InputStreamReader(System.in));
        }
  
        String next()
        {
            while (st == null || !st.hasMoreElements())
            {
                try
                {
                    st = new StringTokenizer(br.readLine());
                }
                catch (IOException  e)
                {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }
  
        int nextInt()
        {
            return Integer.parseInt(next());
        }
  
        long nextLong()
        {
            return Long.parseLong(next());
        }
  
        double nextDouble()
        {
            return Double.parseDouble(next());
        }
  
        String nextLine()
        {
            String str = "";
            try
            {
                str = br.readLine();
            }
            catch (IOException e)
            {
                e.printStackTrace();
            }
            return str;
        }
    }
    static int mod=1000000007;
    static boolean primes[]=new boolean[1000007];
    static ArrayList<Integer> b=new ArrayList<>();
    static boolean seive(int n){
        Arrays.fill(primes,true);
        primes[0]=primes[1]=false;
        for(int i=2;i*i<=n;i++){
            if(primes[i]==true){
                for(int p=i*i;p<=n;p+=i){
                    primes[p]=false;
                }
            }
        }
        if(n<1000007){
        	for(int i=2;i<=n;i++) {
        		if(primes[i])
        			b.add(i);
        	}
            return primes[n];
        }
        return false;
        
    }
    static int gcd(int a,int b){
        if(b==0)
        return a;
        return gcd(b,a%b);
    }
    static long GCD(long a,long b){
        if(b==0)
        return a;
        return GCD(b,a%b);
    }
    static ArrayList<Integer> segseive(int l,int r){
    	
    	ArrayList<Integer> isprime=new ArrayList<Integer>();
    	boolean p[]=new boolean[r-l+1];
    	Arrays.fill(p, true);
        
    	for(int i=0;b.get(i)*b.get(i)<=r;i++) {
    		int currprime=b.get(i);
    		int base=(l/currprime)*currprime;
    		if(base<l) {
    			base+=currprime;
    		}
    		for(int j=base;j<=r;j+=currprime) {
    			p[j-l]=false;
    		}
    		
    		
    		if(base==currprime) {
    			p[base-l]=true;
    		}
    		
    	}
    	for(int i=0;i<=r-l;i++) {
    		if(p[i])
    			isprime.add(i+l);
    	}
    	return isprime;
    }
      static int LowerBound(int a[], int x) { // x is the target value or key
  int l=-1,r=a.length;
  while(l+1<r) {
    int m=(l+r)>>>1;
    if(a[m]>=x) r=m;
    else l=m;
  }
  return r;
}
static int UpperBound(int a[], int x) {// x is the key or target value
    int l=-1,r=a.length;
    while(l+1<r) {
       int m=(l+r)>>>1;
       if(a[m]<=x) l=m;
       else r=m;
    }
    return l+1;
 }

  
     
}