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.util.PriorityQueue;
import java.util.InputMismatchException;
import java.io.IOException;
import java.util.Comparator;
import java.io.InputStream;

/**
 * Built using CHelper plug-in Actual solution is at the top
 *
 * @author MaxHeap
 */
public class Main {

  public static void main(String[] args) {
    InputStream inputStream = System.in;
    OutputStream outputStream = System.out;
    InputReader in = new InputReader(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, InputReader in, PrintWriter out) {
      int n = in.nextInt();
      int k = in.nextInt();
      LongPair[] cds = new LongPair[n];
      for (int i = 0; i < n; ++i) {
        cds[i] = Factories.makeLongPair(in.nextInt(), in.nextInt());
      }
      Arrays.sort(cds, Comparator.comparingLong((LongPair e) -> e.second)
          .thenComparing(e -> e.first));

      long ans = 0;
      long sum = 0;
      PriorityQueue<Long> pq = new PriorityQueue<>();
      for (int i = n - 1; i >= 0; --i) {
        sum += cds[i].first;
        pq.add(cds[i].first);
        while (pq.size() > k) {
          sum -= pq.poll();
        }
        ans = Math.max(ans, sum * cds[i].second);
      }
      out.println(ans);
    }

  }

  static class LongPair implements Comparable<LongPair> {

    public long first;
    public long second;

    public LongPair(long first, long second) {
      this.first = first;
      this.second = second;
    }

    public int compareTo(LongPair a) {
      if (second == a.second) {
        return Long.compare(first, a.first);
      }
      return Long.compare(second, a.second);
    }

    public String toString() {
      return "<" + first + ", " + second + ">";
    }

    public boolean equals(Object o) {
      if (this == o) {
        return true;
      }
      if (o == null || getClass() != o.getClass()) {
        return false;
      }

      LongPair longPair = (LongPair) o;

      if (first != longPair.first) {
        return false;
      }
      return second == longPair.second;
    }

    public int hashCode() {
      long result = (int) (first ^ (first >>> 32));
      result = 31L * result + (second ^ (second >>> 32));
      return (int) (result >>> 10);
    }

  }

  static interface FastIO {

  }

  static final class Factories {

    private Factories() {
    }

    public static LongPair makeLongPair(long first, long second) {
      return new LongPair(
          first, second);
    }

  }

  static class InputReader implements FastIO {

    private InputStream stream;
    private static final int DEFAULT_BUFFER_SIZE = 1 << 16;
    private static final int EOF = -1;
    private byte[] buf = new byte[DEFAULT_BUFFER_SIZE];
    private int curChar;
    private int numChars;

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

    public int read() {
      if (this.numChars == EOF) {
        throw new UnknownError();
      } else {
        if (this.curChar >= this.numChars) {
          this.curChar = 0;

          try {
            this.numChars = this.stream.read(this.buf);
          } catch (IOException ex) {
            throw new InputMismatchException();
          }

          if (this.numChars <= 0) {
            return EOF;
          }
        }

        return this.buf[this.curChar++];
      }
    }

    public int nextInt() {
      int c;
      for (c = this.read(); isSpaceChar(c); c = this.read()) {
      }

      byte sgn = 1;
      if (c == 45) {
        sgn = -1;
        c = this.read();
      }

      int res = 0;

      while (c >= 48 && c <= 57) {
        res *= 10;
        res += c - 48;
        c = this.read();
        if (isSpaceChar(c)) {
          return res * sgn;
        }
      }

      throw new InputMismatchException();
    }

    public static boolean isSpaceChar(int c) {
      return c == 32 || c == 10 || c == 13 || c == 9 || c == EOF;
    }

  }
}