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.*;

public class Main {
    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int M = sc.nextInt();

        List<String> shopList = new ArrayList<String>();
        for (int i=0; i<N; i++) {
            shopList.add(String.format("%09d",sc.nextLong()) + "," + String.format("%09d",sc.nextLong()));
        }
        Collections.sort(shopList);
        Long kingaku = 0L;
        for (String sp : shopList) {
            //System.out.println(sp);
            if (M == 0) {
                break;
            }
            String[] strArray  = sp.split(",");
            Long A = Long.parseLong(strArray[0]);
            Long B = Long.parseLong(strArray[1]);

            if (M <= B) {
                kingaku += A * M;
                M -= M;
            }
            else {
                kingaku += A * B;
                M -= B;
            }

        }
        System.out.println(kingaku);
    }

}