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.*;
import java.util.*;

public class Sol {
	 static class FastReader 
	    { 
	        final private int BUFFER_SIZE = 1 << 16; 
	        private DataInputStream din; 
	        private byte[] buffer; 
	        private int bufferPointer, bytesRead; 
	  
	        public FastReader() 
	        { 
	            din = new DataInputStream(System.in); 
	            buffer = new byte[BUFFER_SIZE]; 
	            bufferPointer = bytesRead = 0; 
	        } 
	  
	        public FastReader(String file_name) throws IOException 
	        { 
	            din = new DataInputStream(new FileInputStream(file_name)); 
	            buffer = new byte[BUFFER_SIZE]; 
	            bufferPointer = bytesRead = 0; 
	        } 
	  
	        public String nextLine() throws IOException 
	        { 
	            byte[] buf = new byte[64]; // line length 
	            int cnt = 0, c; 
	            while ((c = read()) != -1) 
	            { 
	                if (c == '\n') 
	                    break; 
	                buf[cnt++] = (byte) c; 
	            } 
	            return new String(buf, 0, cnt); 
	        } 
	  
	        public int nextInt() throws IOException 
	        { 
	            int ret = 0; 
	            byte c = read(); 
	            while (c <= ' ') 
	                c = read(); 
	            boolean neg = (c == '-'); 
	            if (neg) 
	                c = read(); 
	            do
	            { 
	                ret = ret * 10 + c - '0'; 
	            }  while ((c = read()) >= '0' && c <= '9'); 
	  
	            if (neg) 
	                return -ret; 
	            return ret; 
	        } 
	  
	        public long nextLong() throws IOException 
	        { 
	            long ret = 0; 
	            byte c = read(); 
	            while (c <= ' ') 
	                c = read(); 
	            boolean neg = (c == '-'); 
	            if (neg) 
	                c = read(); 
	            do { 
	                ret = ret * 10 + c - '0'; 
	            } 
	            while ((c = read()) >= '0' && c <= '9'); 
	            if (neg) 
	                return -ret; 
	            return ret; 
	        } 
	  
	        public double nextDouble() throws IOException 
	        { 
	            double ret = 0, div = 1; 
	            byte c = read(); 
	            while (c <= ' ') 
	                c = read(); 
	            boolean neg = (c == '-'); 
	            if (neg) 
	                c = read(); 
	  
	            do { 
	                ret = ret * 10 + c - '0'; 
	            } 
	            while ((c = read()) >= '0' && c <= '9'); 
	  
	            if (c == '.') 
	            { 
	                while ((c = read()) >= '0' && c <= '9') 
	                { 
	                    ret += (c - '0') / (div *= 10); 
	                } 
	            } 
	  
	            if (neg) 
	                return -ret; 
	            return ret; 
	        } 
	  
	        private void fillBuffer() throws IOException 
	        { 
	            bytesRead = din.read(buffer, bufferPointer = 0, BUFFER_SIZE); 
	            if (bytesRead == -1) 
	                buffer[0] = -1; 
	        } 
	  
	        private byte read() throws IOException 
	        { 
	            if (bufferPointer == bytesRead) 
	                fillBuffer(); 
	            return buffer[bufferPointer++]; 
	        } 
	  
	        public void close() throws IOException 
	        { 
	            if (din == null) 
	                return; 
	            din.close(); 
	        } 
	    } 
	  
	public static PrintWriter out = new PrintWriter (new BufferedOutputStream(System.out));
	static final long mod = (long)(1e9+7);
	
	//static Scanner sc = new Scanner(System.in);
	public static void main(String[] args) throws IOException {
		FastReader sc = new FastReader();
		// TODO Auto-generated method stub
		int n = sc.nextInt();
		int k = sc.nextInt();
		int[] t = new int[n];
		int[] b = new int[n];
		Pair[] p = new Pair[n];
		for(int i=0;i<n;++i) {
			t[i] = sc.nextInt();
			b[i] = sc.nextInt();
			p[i] = new Pair(t[i],b[i]);
			
		}
		
		Arrays.sort(p);
		TreeMap<Long,Integer>map=new TreeMap<>();
		long sum=0;
		long ans=0;
		long bs=0;
		for(int i=n-1;i>=0;i--){
			if(bs<k){
				add(map,p[i].first);
				sum+=p[i].first;
				ans=Math.max(ans,sum*p[i].second);
				bs++;
			}else if(p[i].first>map.firstKey()){
				long key=map.firstKey();
				if(map.get(key)==1)
					map.pollFirstEntry();
				else
					map.put(key,map.get(key)-1);
				sum-=key;
				add(map,p[i].first);
				sum+=p[i].first;
				ans=Math.max(ans,sum*p[i].second);
			}
		}
		out.println(ans);
			 out.close();
		}

	private static void add(TreeMap<Long, Integer> map, long first) {
		// TODO Auto-generated method stub
		if(map.containsKey(first)) map.put(first, map.get(first)+1);
		else map.put(first, 1);
		
	}
	
		static class Pair implements Comparable<Pair>{
			long first;
			long second;
			Pair(long first,long second){
				this.first = first;
				this.second = second;
			}
			@Override
			public int compareTo(Pair o) {
				return (int) (second-o.second);
			}
			
		}
		
	
	}