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.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.io.FilterInputStream;
import java.io.BufferedInputStream;
import java.util.Comparator;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author Jenish
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        ScanReader in = new ScanReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        CPlaylist solver = new CPlaylist();
        solver.solve(1, in, out);
        out.close();
    }

    static class CPlaylist {
        public void solve(int testNumber, ScanReader in, PrintWriter out) {
            int n = in.scanInt();
            int k = in.scanInt();
            Songs arr[] = new Songs[n];
            for (int i = 0; i < n; i++) {
                arr[i] = new Songs(in.scanLong(), in.scanLong());
            }

            long ans = 0;
            Arrays.sort(arr, new Comparator<Songs>() {

                public int compare(Songs o1, Songs o2) {
                    return Long.compare(o1.beu, o2.beu);
                }
            });

            AVLTree<Long> avlTree = new AVLTree<>(true);
            long sum = 0;
            int index = -1;
            for (int i = n - 1; i >= 0; i--) {
                long temp = arr[i].beu;
                if (avlTree.getSize() < k) {
                    avlTree.insert(arr[i].len);
                    sum += arr[i].len;
                    ans = Math.max(ans, sum * temp);
                }
                if (avlTree.getSize() == k) {
                    index = i;
                    break;
                }
            }


            for (int i = index - 1; i >= 0; i--) {
                long temp = arr[i].beu;
                if (arr[i].len > avlTree.getMin()) {
                    long min = avlTree.getMin();
                    avlTree.remove(min, 1);
                    sum -= min;
                    sum += arr[i].len;
                    avlTree.insert(arr[i].len);
                }
                ans = Math.max(ans, temp * sum);
            }

            out.println(ans);
        }

        class Songs {
            long len;
            long beu;

            public Songs(long len, long beu) {
                this.len = len;
                this.beu = beu;
            }

        }

    }

    static class AVLTree<T extends Comparable<? super T>> {
        private Node<T> root;
        private boolean multi;
        private Node<T> tempNode;

        public AVLTree() {
            this.root = null;
            this.multi = false;
        }

        public AVLTree(boolean multi) {
            this.root = null;
            this.multi = multi;
        }

        public T getMin() {
            if (root == null) return null;
            tempNode = root;
            while (tempNode.left != null) {
                tempNode = tempNode.left;
            }

            return tempNode.data;
        }

        public long getSize() {
            if (root == null) return 0;
            else {
                return root.leftcount + root.rightcount + root.count;
            }
        }

        public void insert(T data, int... count) {
            if (count.length == 0) root = insert(data, root, 1);
            else {
                if (count[0] > 0) root = insert(data, root, count[0]);
            }
        }

        private Node<T> insert(T data, Node<T> tempRoot, int count) {
            if (tempRoot == null) {
                if (!multi) {

                    return new Node<>(data);
                } else {

                    return new Node<>(data, count);
                }
            }


            int compartor = data.compareTo(tempRoot.data);
            if (compartor < 0) {
                tempRoot.left = insert(data, tempRoot.left, count);
            } else if (compartor > 0) {
                tempRoot.right = insert(data, tempRoot.right, count);
            } else {
                if (multi) {
                    tempRoot.count += count;
                }
            }


            tempRoot.leftcount = getLeftCount(tempRoot.left) + getRightCount(tempRoot.left) + getCount(tempRoot.left);
            tempRoot.rightcount = getLeftCount(tempRoot.right) + getRightCount(tempRoot.right) + getCount(tempRoot.right);


            tempRoot.height = Math.max(Hieght(tempRoot.left), Hieght(tempRoot.right)) + 1;


            long diff = getBalence(tempRoot);

            if (diff > 1) {
                if (data.compareTo(tempRoot.left.data) < 0) {
                    return rotateRight(tempRoot);
                } else {
                    tempRoot.left = rotateLeft(tempRoot.left);
                    return rotateRight(tempRoot);
                }
            } else if (diff < -1) {
                if (data.compareTo(tempRoot.right.data) > 0) {
                    return rotateLeft(tempRoot);
                } else {
                    tempRoot.right = rotateRight(tempRoot.right);
                    return rotateLeft(tempRoot);
                }
            }

            return tempRoot;


        }

        public Node<T> rotateRight(Node<T> node) {
            Node<T> x = node.left;
            Node<T> t2 = x.right;


            x.right = node;
            node.left = t2;


            node.height = Math.max(Hieght(node.right), Hieght(node.left)) + 1;
            x.height = Math.max(Hieght(x.left), Hieght(x.right)) + 1;


            node.leftcount = getLeftCount(node.left) + getRightCount(node.left) + getCount(node.left);
            node.rightcount = getLeftCount(node.right) + getRightCount(node.right) + getCount(node.right);


            x.leftcount = getLeftCount(x.left) + getRightCount(x.left) + getCount(x.left);
            x.rightcount = getLeftCount(x.right) + getRightCount(x.right) + getCount(x.right);

            return x;

        }

        public Node<T> rotateLeft(Node<T> node) {
            Node<T> x = node.right;
            Node<T> t2 = x.left;


            x.left = node;
            node.right = t2;


            node.height = Math.max(Hieght(node.right), Hieght(node.left)) + 1;
            x.height = Math.max(Hieght(x.left), Hieght(x.right)) + 1;


            node.leftcount = getLeftCount(node.left) + getRightCount(node.left) + getCount(node.left);
            node.rightcount = getLeftCount(node.right) + getRightCount(node.right) + getCount(node.right);


            x.leftcount = getLeftCount(x.left) + getRightCount(x.left) + getCount(x.left);
            x.rightcount = getLeftCount(x.right) + getRightCount(x.right) + getCount(x.right);

            return x;

        }

        public long getLeftCount(Node<T> node) {
            if (node == null) return 0;
            return node.leftcount;
        }

        public long getRightCount(Node<T> node) {
            if (node == null) return 0;
            return node.rightcount;
        }

        public long getCount(Node<T> node) {
            if (node == null) return 0;
            return node.count;
        }

        long getBalence(Node<T> node) {
            if (node == null)
                return 0;

            return Hieght(node.left) - Hieght(node.right);
        }

        public long Hieght(Node<T> Node) {
            if (Node == null) return 0;
            else return Node.height;
        }

        public void remove(T data, int c) {
            if (c > 0) root = remove(root, data, c);
        }

        private Node<T> remove(Node<T> tempRoot, T data, long num) {


            if (tempRoot == null) return null;
            int compartor = data.compareTo(tempRoot.data);
            if (compartor < 0) {
                tempRoot.left = remove(tempRoot.left, data, num);
            } else if (compartor > 0) {
                tempRoot.right = remove(tempRoot.right, data, num);
            } else {
                if (multi && num < tempRoot.count && tempRoot.count > 1) {
                    tempRoot.count -= num;
                } else {
                    if (tempRoot.left == null && tempRoot.right == null) {
                        return null;
                    } else if (tempRoot.left == null) return tempRoot.right;
                    else if (tempRoot.right == null) return tempRoot.left;
                    else {
                        Node<T> minValueNode = getMinValueNode(tempRoot.right);

                        tempRoot.data = minValueNode.data;
                        tempRoot.count = minValueNode.count;

                        tempRoot.right = remove(tempRoot.right, tempRoot.data, tempRoot.count);
                    }

                }
            }


            tempRoot.leftcount = getLeftCount(tempRoot.left) + getRightCount(tempRoot.left) + getCount(tempRoot.left);
            tempRoot.rightcount = getLeftCount(tempRoot.right) + getRightCount(tempRoot.right) + getCount(tempRoot.right);

            tempRoot.height = Math.max(Hieght(tempRoot.left), Hieght(tempRoot.right)) + 1;


            long diff = getBalence(tempRoot);

            if (diff > 1) {
                if (getBalence(tempRoot.left) >= 0) {
                    return rotateRight(tempRoot);
                } else {
                    tempRoot.left = rotateLeft(tempRoot.left);
                    return rotateRight(tempRoot);
                }
            } else if (diff < -1) {
                if (getBalence(tempRoot.right) <= 0) {
                    return rotateLeft(tempRoot);
                } else {
                    tempRoot.right = rotateRight(tempRoot.right);
                    return rotateLeft(tempRoot);
                }
            }

            return tempRoot;
        }

        public Node<T> getMinValueNode(Node<T> node) {
            if (node == null) return null;
            Node<T> currentNode = node;
            while (currentNode.left != null) {
                currentNode = currentNode.left;
            }
            return currentNode;
        }

        public class Node<T> {
            T data;
            long height;
            Node<T> left;
            Node<T> right;
            long leftcount;
            long rightcount;
            long count;

            public Node(T data) {
                this.data = data;
                this.height = 1;
                this.left = null;
                this.right = null;
                this.leftcount = 0;
                this.rightcount = 0;
                this.count = 1;
            }

            public Node(T data, int count) {
                this.data = data;
                this.height = 1;
                this.left = null;
                this.right = null;
                this.leftcount = 0;
                this.rightcount = 0;
                this.count = count;
            }

        }

    }

    static class ScanReader {
        private byte[] buf = new byte[4 * 1024];
        private int INDEX;
        private BufferedInputStream in;
        private int TOTAL;

        public ScanReader(InputStream inputStream) {
            in = new BufferedInputStream(inputStream);
        }

        private int scan() {
            if (INDEX >= TOTAL) {
                INDEX = 0;
                try {
                    TOTAL = in.read(buf);
                } catch (Exception e) {
                    e.printStackTrace();
                }
                if (TOTAL <= 0) return -1;
            }
            return buf[INDEX++];
        }

        public int scanInt() {
            int I = 0;
            int n = scan();
            while (isWhiteSpace(n)) n = scan();
            int neg = 1;
            if (n == '-') {
                neg = -1;
                n = scan();
            }
            while (!isWhiteSpace(n)) {
                if (n >= '0' && n <= '9') {
                    I *= 10;
                    I += n - '0';
                    n = scan();
                }
            }
            return neg * I;
        }

        private boolean isWhiteSpace(int n) {
            if (n == ' ' || n == '\n' || n == '\r' || n == '\t' || n == -1) return true;
            else return false;
        }

        public long scanLong() {
            long I = 0;
            int n = scan();
            while (isWhiteSpace(n)) n = scan();
            int neg = 1;
            if (n == '-') {
                neg = -1;
                n = scan();
            }
            while (!isWhiteSpace(n)) {
                if (n >= '0' && n <= '9') {
                    I *= 10;
                    I += n - '0';
                    n = scan();
                }
            }
            return neg * I;
        }

    }
}