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.
//package year2019.month03.cf.eduround62div2;

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.*;

public class eduround62div2CC {

    boolean ONLINE_JUDGE = (System.getProperty("ONLINE_JUDGE") != null);

    public eduround62div2CC() throws IOException {
        InputReader in;
        if (ONLINE_JUDGE) {
            in = new InputReader(System.in);
        } else {
            in = new InputReader(new FileInputStream("/Users/karj/cp/input.txt"));
        }
        PrintWriter out = new PrintWriter(System.out);

        int T = 1;
        for (int caseNo = 1; caseNo <= T; caseNo++) {
            solve(caseNo, in, out);
        }

        out.close();
    }

    private void solve(int caseNo, InputReader in, PrintWriter out) throws IOException {
        int n = in.nextInt(), k = in.nextInt();
        Pair<Long, Long> s[] = new Pair[n];
        for (int i = 0; i < n; i++) {
            s[i] = new Pair<>(in.nextLong(), in.nextLong());
        }
        Arrays.sort(s, (o1, o2) -> Long.compare(o2.s, o1.s));
        long ans = 0, sum = 0, beauty = 0;
        PriorityQueue<Pair<Long, Long>> pq = new PriorityQueue<>((o1, o2) -> Long.compare(o1.f, o2.f));
        for (int i = 0; i < n; i++) {
            beauty = s[i].s;
            if (pq.size() < k) {
                sum += s[i].f;
                pq.add(s[i]);
            } else if (pq.peek().f < s[i].f) {
                sum -= pq.poll().f;
                sum += s[i].f;
                pq.add(s[i]);
            }
            ans = max(ans, sum * beauty);
        }
        out.println(ans);
    }

    static class InputReader {

        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
        private SpaceCharFilter filter;

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

        public static boolean isWhitespace(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        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 boolean isSpaceChar(int c) {
            if (filter != null) {
                return filter.isSpaceChar(c);
            }
            return isWhitespace(c);
        }

        public interface SpaceCharFilter {

            public boolean isSpaceChar(int ch);
        }

        public String next() {
            return nextString();
        }

        public String nextString() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            StringBuilder res = new StringBuilder();
            do {
                res.appendCodePoint(c);
                c = read();
            } while (!isSpaceChar(c));
            return res.toString();
        }

        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 Long nextLong() {
            return Long.parseLong(nextString());
        }

        public Double nextDouble() {
            return Double.parseDouble(nextString());
        }

        public char nextCharacter() {
            return nextString().charAt(0);
        }

        public int[] nextIntArray(int N) {
            int A[] = new int[N];
            for (int i = 0; i < N; i++) {
                A[i] = nextInt();
            }
            return A;
        }

        public long[] nextLongArray(int N) {
            long A[] = new long[N];
            for (int i = 0; i < N; i++) {
                A[i] = nextLong();
            }
            return A;
        }

        public double[] nextDoubleArray(int N) {
            double A[] = new double[N];
            for (int i = 0; i < N; i++) {
                A[i] = nextDouble();
            }
            return A;
        }
    }

    int min(int... a) {
        int min = Integer.MAX_VALUE;
        for (int v : a) {
            min = Math.min(min, v);
        }
        return min;
    }

    long min(long... a) {
        long min = Long.MAX_VALUE;
        for (long v : a) {
            min = Math.min(min, v);
        }
        return min;
    }

    double min(double... a) {
        double min = Double.MAX_VALUE;
        for (double v : a) {
            min = Math.min(min, v);
        }
        return min;
    }

    int max(int... a) {
        int max = Integer.MIN_VALUE;
        for (int v : a) {
            max = Math.max(max, v);
        }
        return max;
    }

    long max(long... a) {
        long max = Long.MIN_VALUE;
        for (long v : a) {
            max = Math.max(max, v);
        }
        return max;
    }

    double max(double... a) {
        double max = Double.MIN_VALUE;
        for (double v : a) {
            max = Math.max(max, v);
        }
        return max;
    }

    public <A, B> Pair MP(A a, B b) {
        return new Pair<A, B>(a, b);
    }

    class Pair<F, S> {
        public final F f;
        public final S s;

        public Pair(F f, S s) {
            this.f = f;
            this.s = s;
        }

        @Override
        public boolean equals(Object o) {
            if (this == o) return true;
            if (o == null || getClass() != o.getClass()) return false;
            Pair<?, ?> pair = (Pair<?, ?>) o;
            return Objects.equals(f, pair.f) &&
                    Objects.equals(s, pair.s);
        }

        @Override
        public int hashCode() {

            return Objects.hash(f, s);
        }

        @Override
        public String toString() {
            return f.toString() + " " + s.toString();
        }
    }


    private void debug(Object... o) {
        if (ONLINE_JUDGE) {
            return;
        }
        System.err.println(Arrays.deepToString(o));
    }

    public static void main(String args[]) throws IOException {
        new eduround62div2CC();
    }
}
