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.OutputStream;
import java.io.PrintWriter;
import java.io.BufferedWriter;
import java.util.InputMismatchException;
import java.io.IOException;
import java.util.ArrayList;
import java.io.Writer;
import java.io.OutputStreamWriter;
import java.util.Comparator;
import java.util.Collections;
import java.io.InputStream;

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

    static class TaskC {
        static int[] t;
        static int[] b;

        public void solve(int testNumber, InputReader in, OutputWriter out) {
            int n = in.nextInt(), k = in.nextInt();
            t = new int[n + 1];
            b = new int[n + 1];
            int[] indices = new int[n + 1];
            ArrayList<intWrapper> perm = new ArrayList<>();
            ArrayList<intWrapper> perm2 = new ArrayList<>();
            for (int i = 1; i <= n; i++) {
                t[i] = in.nextInt();
                b[i] = in.nextInt();
                perm.add(new intWrapper(i));
                perm2.add(new intWrapper(i));
            }
            Collections.shuffle(perm);
            Collections.sort(perm, new TaskC.intComparator());
            Collections.shuffle(perm2);
            Collections.sort(perm2, new TaskC.intComparator2());
            for (int i = 1; i <= n; i++) {
                indices[perm2.get(i - 1)._ind] = i;
            }
            TaskC.segtree tree = new TaskC.segtree(n);
            long ans = 0;
            for (int i = n - 1; i >= 0; i--) {
                int ind = perm.get(i)._ind;
                tree.update(1, n, indices[ind], t[ind], 1);
                ans = Long.max(ans, tree.getK(1, n, Integer.min(n - i, k), 1) * (new Long(b[ind])));
            }
            out.println(ans);
        }

        public class intWrapper {
            int _ind;

            public intWrapper() {

            }

            public intWrapper(int v) {
                _ind = v;
            }

        }

        static class intComparator implements Comparator<intWrapper> {
            public int compare(intWrapper x, intWrapper y) {
                return (new Integer(b[x._ind])).compareTo(new Integer(b[y._ind]));
            }

        }

        static class intComparator2 implements Comparator<intWrapper> {
            public int compare(intWrapper x, intWrapper y) {
                return (new Integer(t[x._ind])).compareTo(new Integer(t[y._ind]));
            }

        }

        static class segtree {
            long[] st;
            int[] count;

            segtree(int n) {
                st = new long[4 * n + 10];
                count = new int[4 * n + 10];
            }

            void update(int s, int e, int i, int v, int ind) {
                if (s > i || e < i) return;
                count[ind]++;
                st[ind] += v;
                if (s == e) return;
                int mid = (s + e) / 2;
                if (i <= mid) update(s, mid, i, v, ind * 2);
                else update(mid + 1, e, i, v, ind * 2 + 1);
            }

            long getK(int s, int e, int k, int ind) {
                if (k == 0) return 0;
                if (s == e) return st[ind];
                int mid = (s + e) / 2;
                if (count[2 * ind + 1] >= k) return getK(mid + 1, e, k, 2 * ind + 1);
                return st[2 * ind + 1] + getK(s, mid, k - count[2 * ind + 1], 2 * ind);
            }

        }

    }

    static class OutputWriter {
        private final PrintWriter writer;

        public OutputWriter(OutputStream outputStream) {
            writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
        }

        public OutputWriter(Writer writer) {
            this.writer = new PrintWriter(writer);
        }

        public void println(Object... objects) {
            for (int i = 0; i < objects.length; i++) {
                if (i != 0) {
                    writer.print(' ');
                }
                writer.print(objects[i]);
            }
            writer.print('\n');
        }

        public void close() {
            writer.close();
        }

    }

    static class InputReader {
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
        private InputReader.SpaceCharFilter filter;

        public InputReader(InputStream stream) {
            this.stream = stream;
        }

        public int read() {
            if (numChars == -1) throw new InputMismatchException();
            if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (numChars <= 0) return -1;
            }
            return buf[curChar++];
        }

        public int nextInt() {
            int c = read();
            while (isSpaceChar(c)) c = read();
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            int res = 0;
            do {
                if (c < '0' || c > '9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        }

        public boolean isSpaceChar(int c) {
            if (filter != null)
                return filter.isSpaceChar(c);
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        public interface SpaceCharFilter {
            boolean isSpaceChar(int ch);

        }

    }
}