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:
// https://codeforces.com/contest/1140/problem/C
import java.util.*;
import java.io.*;

public class Solution_1140_C {

    static class Song {
        int t;
        int b;

        public Song() {

        }

        public Song(int t, int b) {
            this.t = t;
            this.b = b;
        }
        
        public String toString() {
            return "{" + this.t + " " + this.b + "}";
        }
        
    }

    static class Comparators {
        public static Comparator<Song> BEAUTY = new Comparator<Song>() {
            @Override
            public int compare(Song a, Song b) {
                if (a.b > b.b) {
                    return -1;
                }
                else if (a.b < b.b) {
                    return 1;
                }
                else {
                    return 0;
                }
            }
        };

        public static Comparator<Song> LENGTH = new Comparator<Song>() {
            @Override
            public int compare(Song a, Song b) {
                if (a.t < b.t) {
                    return -1;
                }
                else if (a.t > b.t) {
                    return 1;
                }
                else {
                    return 0;
                }
            }
        };
    }

    /* The data structure that will maintain the maximum sum of song length
        that is possible for a beauty that is smallest */
    static class SongSet {
        private PriorityQueue<Song> pq;

        public long sum;
        public Song minLengthSong;
        
        public SongSet() {
            pq = new PriorityQueue<>(Comparators.LENGTH);
            sum = 0;
            minLengthSong = null;
        }

        public void insertSong(Song s) {
            pq.add(s);
            
            sum += s.t;

            /* update minLengthSong */
            if(minLengthSong == null) {
                minLengthSong = pq.peek();
            }
            else {
                if(Comparators.LENGTH.compare(s, minLengthSong) < 0) {
                    minLengthSong = s;
                }
            }
        }

        public void removeMinLengthSong() {
            Song removed = pq.remove();

            sum -= removed.t;

            /* update minLengthSong */
            minLengthSong = pq.peek();
        }
        
        public int songCount() {
            return pq.size();
        }

        public String toString() {
            return pq.toString();
        }
    }

    static BufferedReader in;
    static FastScanner sc;
    static PrintWriter out;

    static int n;
    static int k;
    static List<Song> songs;

    /* The actual algorithm */
    public static void solve() {
        Collections.sort(songs, Comparators.BEAUTY);
        SongSet o = new SongSet();
        long result = 0;
        for(Song s : songs) {
            if(o.songCount() == k) {
                Song mn = o.minLengthSong;
                if(Comparators.LENGTH.compare(mn, s) < 0) {
                    o.removeMinLengthSong();
                    o.insertSong(s);
                    long currPleasure = o.sum * s.b;
                    result = Math.max(currPleasure, result);
                }
            }
            else {
                o.insertSong(s);
                long currPleasure = o.sum * s.b;
                result = Math.max(currPleasure, result);
            }
        }
        out.println(result);
    }
    public static void main(String[] args) throws Exception {
        in = new BufferedReader(new InputStreamReader(System.in));
        FastScanner sc = new FastScanner(in);
        out = new PrintWriter(System.out);
        n = sc.nextInt();
        k = sc.nextInt();
        songs = new ArrayList<>();
        for(int i = 0; i < n; i++) {
            int ti = sc.nextInt();
            int bi = sc.nextInt();
            songs.add(new Song(ti, bi));
        }

        solve();

        out.close();
    }
}

/* Class that simulates Scanner - but Faster?(taken from user on CodeForces) */
class FastScanner {
    BufferedReader in;
    StringTokenizer st;

    public FastScanner(BufferedReader in) {
        this.in = in;
    }

    public String nextToken() throws Exception {
        while (st == null || !st.hasMoreTokens()) {
            st = new StringTokenizer(in.readLine());
        }
        return st.nextToken();
    }

    public int nextInt() throws Exception {
        return Integer.parseInt(nextToken());
    }

    public long nextLong() throws Exception {
        return Long.parseLong(nextToken());
    }

    public double nextDouble() throws Exception {
        return Double.parseDouble(nextToken());
    }
}