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.*;
import java.lang.*;
import java.math.*;
public final  class Main{
    public static boolean[] prime;
    public static class Job implements Comparable<Job>{
        int l;
        int b;
        public Job(int x,int y)
        {
            l=x;
            b=y;
        }
        public int compareTo(Job b)
        {
            return b.b-this.b;
        }
    }
    public static final class FastScanner {
        BufferedReader br;
        StringTokenizer st;

        public FastScanner() {
            try {
                br = new BufferedReader(new InputStreamReader(System.in));
                st = new StringTokenizer(br.readLine());
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        public long nextLong() {
            return Long.parseLong(next());
        }
        public String next() {
            if (st.hasMoreTokens()) return st.nextToken();
            try {
                st = new StringTokenizer(br.readLine());
            } catch (Exception e) {
                e.printStackTrace();
            }
            return st.nextToken();
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }
        public String nextLine() {
            String line = "";
            if (st.hasMoreTokens()) line = st.nextToken();
            else try {
                return br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            while (st.hasMoreTokens()) line += " " + st.nextToken();
            return line;
        }
        public double nextDouble() {
            return Double.parseDouble(next());
        }
    }
    public static final class MathFunction{
        public static long gcd(long a, long b) {
            long var;
            while (a % b > 0) {
                var = b;
                b = a % b;
                a = var;
            }
            return b;
        }
        public static int nod(long x)
        {
            int i=0;
            while(x!=0)
            {
                i++;
                x=x/10;
            }
            return i;
        }
        public static int nob(long x)
        {
            return (int)Math.floor(Math.log(x)/Math.log(2))+1;
        }
        public static int[] FastradixSort(int[] f)
        {
            int[] to = new int[f.length];
            {
                int[] b = new int[65537];
                for(int i = 0;i < f.length;i++)b[1+(f[i]&0xffff)]++;
                for(int i = 1;i <= 65536;i++)b[i]+=b[i-1];
                for(int i = 0;i < f.length;i++)to[b[f[i]&0xffff]++] = f[i];
                int[] d = f; f = to;to = d;
            }
            {
                int[] b = new int[65537];
                for(int i = 0;i < f.length;i++)b[1+(f[i]>>>16)]++;
                for(int i = 1;i <= 65536;i++)b[i]+=b[i-1];
                for(int i = 0;i < f.length;i++)to[b[f[i]>>>16]++] = f[i];
                int[] d = f; f = to;to = d;
            }
            return f;
        }
        public static void Primesieve(int n) {
            for (int i = 0; i < n; i++)
                prime[i] = true;
            for (int p = 2; p * p < n; p++) {
                if (prime[p] == true) {
                    for (int i = p * p; i < n; i += p)
                        prime[i] = false;
                }
            }
        }
    }
    public static void main(String args[]) {
        FastScanner sc = new FastScanner();
        PrintWriter pw = new PrintWriter(System.out);
        int n,t, i, k, m, j;
        n=sc.nextInt();
        k=sc.nextInt();
        long sum=0,ans=0;
        List<Job> list=new ArrayList<Job>();
        for(i=0;i<n;i++)
        {
            t=sc.nextInt();
            m=sc.nextInt();
            list.add(new Job(t,m));
        }
        Collections.sort(list);
        PriorityQueue<Integer> pq=new PriorityQueue<Integer>();
        for(i=0;i<n;i++)
        {
            pq.add(list.get(i).l);
            sum+=list.get(i).l;
            if(pq.size()>k)
            {
                sum-=pq.poll();
            }
            ans=Math.max(ans,list.get(i).b*sum);
        }
        pw.print(ans);
        pw.close();
    }
}