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.Comparator;
import java.util.Scanner;
public class Main{
	public static void main(String[]args){
	Scanner scan=new Scanner(System.in);
	int a=scan.nextInt();
	int b=scan.nextInt();
	long count=0;
	long ans=0;
	int AB[][]=new int[a][2];
	for(int i=0;i<a;i++) {
		int x=scan.nextInt();
		int y=scan.nextInt();
		AB[i][0]=x;
		AB[i][1]=y;
	}
	  Arrays.sort(AB, new Comparator<int[]>() {
	        @Override
	        public int compare(int[] o1, int[] o2) {
	            return o1[0] - o2[0];
	        }
	    });
	  for(int i=0;i!=a;i++) {
		  if((count+AB[i][1])>b) {
			  ans+=(long)AB[i][0]*(b-count);
			  break;
		  }
		  else {
			  count+=AB[i][1];
			  ans+=(long)AB[i][0]*(long)AB[i][1];
		  }
	  }
	  System.out.println(ans);
	}
}