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 {
	
	static class Drinks implements Comparable<Drinks>{
		long cost, drinks;
		public Drinks (long c, long d) {
			cost = c;
			drinks = d;
		}
		@Override
		public int compareTo(Drinks o) {
			// TODO Auto-generated method stub
			return (int) (cost - o.cost);
		}
	}
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long N = sc.nextInt(), M = sc.nextInt(), cost = 0;
		PriorityQueue<Drinks> q = new PriorityQueue<Drinks>();
		for (int i = 0; i < N; i++) {
			long a = sc.nextLong();
			long b = sc.nextLong();
			q.add(new Drinks(a, b));
		}
		for (int i = 0; i < N; i++) {
			Drinks p = q.poll();
			long c = p.cost, d = p.drinks;
			if (M - d < 0) {
				cost += c*M;
				M = 0;
			}
			else {
				cost += c*d;
				M -= d;
			}
			if (M == 0) break;
		}
		System.out.println(cost);
	}

}