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:
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 */

import java.io.IOException;
import java.io.InputStream;
import java.math.BigInteger;
import java.util.*;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
import java.util.stream.Stream;

import static java.lang.Math.max;
import static java.lang.Math.min;
import static java.lang.Math.pow;
import static java.lang.Math.abs;

import static java.lang.String.format;


public class Main {
    final static int INF = Integer.MAX_VALUE >> 1;
    final static int MOD = 1_000_000_007;
    final static int[] dx4 = {0, 1, 0, -1};
    final static int[] dy4 = {1, 0, -1, 0};
    final static int[] dx8 = {0, 1, 1, 1, 0, -1, -1, -1};
    final static int[] dy8 = {1, 1, 0, -1, -1, -1, 0, 1};

    public static void main(String[] args) {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        int k = sc.nextInt();
        List<FixedLongPair> list = new ArrayList<>();
        for (int i = 0; i < n; i++) {
            list.add(new FixedLongPair(sc.nextInt(), sc.nextInt()));
        }
        PriorityQueue<FixedLongPair> bMin=new PriorityQueue<>(Comparator.comparing(flp->flp.x));
        Collections.sort(list,Comparator.comparing(flp->-flp.y));
        long tSum=0;
        long ans=0;
        for (FixedLongPair flp : list) {
            bMin.add(flp);
            tSum+=flp.x;
            while(bMin.size()>k){
                tSum-=bMin.poll().x;
            }
            ans=max(ans,tSum*flp.y);
            //putE(bMin);
        }
        put(ans);
    }


    public static void print(Object object) {
        System.out.print(object);
    }

    public static void put(Object object) {
        System.out.println(object);
    }

    public static void put() {
        System.out.println();
    }

    public static void printE(Object object) {
        System.err.print("DEBUG:" + object);
    }

    public static void putE(Object object) {
        System.err.println("DEBUG:" + object);
    }

    public static void putE() {
        System.err.println("DEBUG:");
    }

    public static void print(String format, Object... args) {
        System.out.print(String.format(format, args));
    }

    public static void put(String format, Object... args) {
        System.out.println(String.format(format, args));
    }

    public static void printE(String format, Object... args) {
        System.err.print("DEBUG:" + String.format(format, args));
    }

    public static void putE(String format, Object... args) {
        System.err.println("DEBUG:" + String.format(format, args));
    }

    final static private class Scanner {
        private final InputStream in = System.in;
        private final byte[] buffer = new byte[1024];
        private int ptr = 0;
        private int buflen = 0;

        private boolean hasNextByte() {
            if (ptr < buflen) {
                return true;
            } else {
                ptr = 0;
                try {
                    buflen = in.read(buffer);
                } catch (IOException e) {
                    e.printStackTrace();
                }
                if (buflen <= 0) {
                    return false;
                }
            }
            return true;
        }

        private int readByte() {
            if (hasNextByte())
                return buffer[ptr++];
            else
                return -1;
        }

        private boolean isPrintableChar(int c) {
            return 33 <= c && c <= 126;
        }

        public boolean hasNext() {
            while (hasNextByte() && !isPrintableChar(buffer[ptr]))
                ptr++;
            return hasNextByte();
        }

        public String next() {
            if (!hasNext())
                throw new NoSuchElementException();
            StringBuilder sb = new StringBuilder();
            int b = readByte();
            while (isPrintableChar(b)) {
                sb.appendCodePoint(b);
                b = readByte();
            }
            return sb.toString();
        }

        public long nextLong() {
            if (!hasNext())
                throw new NoSuchElementException();
            long n = 0;
            boolean minus = false;
            int b = readByte();
            if (b == '-') {
                minus = true;
                b = readByte();
            }
            if (b < '0' || '9' < b) {
                throw new NumberFormatException();
            }
            while (true) {
                if ('0' <= b && b <= '9') {
                    n *= 10;
                    n += b - '0';
                } else if (b == -1 || !isPrintableChar(b)) {
                    return minus ? -n : n;
                } else {
                    throw new NumberFormatException();
                }
                b = readByte();
            }
        }

        public int nextInt() {
            long nl = nextLong();
            if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE)
                throw new NumberFormatException();
            return (int) nl;
        }

        public double nextDouble() {
            return Double.parseDouble(next());
        }
    }

    final static private class FixedIntPair {
        final public int x, y,id;
        static int num=0;
        final static public FixedIntPair ZEROS = new FixedIntPair(0, 0);

        FixedIntPair(int x, int y) {
            this.x = x;
            this.y = y;
            this.id=num++;
        }

        public static double distance(FixedIntPair fip1, FixedIntPair fip2) {
            double x = (double) fip1.x - fip2.x;
            double y = (double) fip1.y - fip2.y;
            return Math.sqrt(x * x + y * y);
        }

        @Override
        public int hashCode() {
            return x + y;
        }


        @Override
        public String toString() {
            return String.format(FixedIntPair.class.getSimpleName() + ":(%d,%d)", x, y);
        }
    }

    final static private class FixedLongPair {
        final public long x, y,id;
        static int num=0;
        final static public FixedLongPair ZEROS = new FixedLongPair(0, 0);

        FixedLongPair(long x, long y) {
            this.x = x;
            this.y = y;
            this.id=num++;
        }

        public static double distance(FixedLongPair flp1, FixedLongPair flp2) {
            double x = (double) flp1.x - flp2.x;
            double y = (double) flp1.y - flp2.y;
            return Math.sqrt(x * x + y * y);
        }

        @Override
        public int hashCode() {
            return (int) x + (int) y;
        }


        @Override
        public String toString() {
            return String.format(FixedLongPair.class.getSimpleName() + ":(%d,%d)", x, y);
        }
    }

    final static private class Binary {
        public static String toZeroPadding(int i) {
            return String.format("%" + Integer.toBinaryString(-1).length() + "s", Integer.toBinaryString(i)).replace(' ', '0');
        }

        public static String toZeroPadding(long i) {
            return String.format("%" + Long.toBinaryString(-1).length() + "s", Long.toBinaryString(i)).replace(' ', '0');
        }
    }

    final static private class Util {
        static long gcd(long a, long b) {
            //最大公約数　
            if (a % b == 0) return b;
            return gcd(b, a % b);
        }

        static long lcm(long a, long b) {
            //最小公倍数
            long gcd = gcd(a, b);
            long result = b / gcd;
            return a * result;
        }

        static <T extends Comparable<T>> Map<T, Integer> count(List<T> list) {
            //副作用
            Collections.sort(list);
            Map<T, Integer> result = new HashMap<>();
            int l = 0, r = 0;
            while (l < list.size()) {
                while (r < list.size() - 1 && list.get(r).equals(r + 1)) {
                    r++;
                }
                result.put(list.get(r), r - l + 1);
                r++;
                l = r;
            }
            return result;

        }

        static Map<Integer, Integer> count(int[] array) {
            //副作用
            Arrays.sort(array);
            Map<Integer, Integer> result = new HashMap<>();
            int l = 0, r = 0;
            while (l < array.length) {
                while (r < array.length - 1 && array[r] == array[r + 1]) {
                    r++;
                }
                result.put(array[l], r - l + 1);
                r++;
                l = r;
            }
            return result;
        }

        static <T> String toStringBWS(Iterable<T> iterable) {
            Iterator<T> ite = iterable.iterator();
            return toStringBWS(ite);
        }

        static <T> String toStringBWS(Iterator<T> ite) {
            StringBuilder sb = new StringBuilder();
            sb.append(ite.next());
            while (ite.hasNext()) {
                sb.append(" ");
                sb.append(ite.next());
            }
            return sb.toString();
        }

        static long factoringInPrimeNumbers(long n, int[] a) {
            //素因数分解
            for (int i = 2; n > 1 && i < a.length; i++) {
                while (n % i == 0) {
                    a[i]++;
                    n /= i;
                }
            }
            return n;

        }

        static boolean isValidCell(int i, int j, int h, int w) {
            return i >= 0 && i < h && j >= 0 && j < w;
        }
    }
}