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.ArrayList;
import java.util.Collections;
import java.util.Scanner;

public class Main {

    public static void main(String[] args){

        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int m = sc.nextInt();
        ArrayList<D> l = new ArrayList<>();
        for(int i=0; i<n; i++) {
            long p = sc.nextLong();
            int num = sc.nextInt();
            l.add(new D(num, p));
        }
        Collections.sort(l);
        long res = 0;
        for(D d : l) {
            if(m > d.num) {
                res += d.num * d.p;
                m -= d.num;
            } else {
                res += m * d.p;
                break;
            }
        }
        System.out.println(res);

    }

    static class D implements Comparable<D> {
        int num;
        long p;
        D(int num, long p) {
            this.num = num;
            this.p = p;
        }

        @Override public int compareTo(D o) {
            if(p<o.p) return -1;
            if(p>o.p) return 1;
            return 0;
        }
    }
}