Problem: Hearing that energy drinks increase rating in those sites, Takahashi decides to buy up M cans of energy drinks.

There are N stores that sell energy drinks. In the i-th store, he can buy at most B_i cans of energy drinks for A_i yen (the currency of Japan) each.

What is the minimum amount of money with which he can buy M cans of energy drinks?

It is guaranteed that, in the given inputs, a sufficient amount of money can always buy M cans of energy drinks.

Constraints

* All values in input are integers.
* 1 \leq N, M \leq 10^5
* 1 \leq A_i \leq 10^9
* 1 \leq B_i \leq 10^5
* B_1 + ... + B_N \geq M

Input

Input is given from Standard Input in the following format:


N M
A_1 B_1
A_2 B_2
\vdots
A_N B_N


Output

Print the minimum amount of money with which Takahashi can buy M cans of energy drinks.

Examples

Input

2 5
4 9
2 4


Output

12


Input

4 30
6 18
2 5
3 10
7 9


Output

130


Input

1 100000
1000000000 100000


Output

100000000000000

Solution (in JAVA):

Solution:

import java.util.Arrays;
import java.util.Scanner;

public class Main {

    void run() {
        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt(), m = sc.nextInt();
        V[] vs = new V[n];

        for (int i = 0; i < n; i++) {
            vs[i] = new V(sc.nextInt(), sc.nextInt());
        }

        Arrays.sort(vs);

        long ret = 0;
        for (int i = 0;m > 0;i++) {
            if (m >= vs[i].b) {
                ret += 1L * vs[i].a * vs[i].b;
                m -= vs[i].b;
            } else {
                ret += 1L * vs[i].a * m;
                m = 0;
            }
        }

        System.out.println(ret);
    }

    class V implements Comparable<V> {

        int a, b;

        V(int a, int b) {
            this.a = a;
            this.b = b;
        }

        @Override
        public int compareTo(V o) {
            return a - o.a;
        }
    }

    public static void main(String[] args) {
        new Main().run();
    }
}