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();
        int[][] nums=new int[n][2];
        for(int i=0;i<n;i++){
            nums[i][0]=sc.nextInt();
            nums[i][1]=sc.nextInt();
        }
        
        Comp comp=new Comp();
        comp.setIndex(0);
        Arrays.sort(nums,comp);
        long[][] nums2=new long[n][2];
        for(int i=0;i<n;i++){
            nums2[i][0]=nums[i][0];
            nums2[i][1]=nums[i][1];
        }
        long output=0;
        long tmp;
        for(int i=0;i<n;i++){
            tmp=Math.min(nums[i][1],m);
            m-=tmp;
            output+=nums[i][0]*tmp;
            if(m==0)break;
            
        }
        System.out.println(output);

    }
    

}
class Comp implements Comparator{
    int index=0;
    void setIndex(int i){
        index=i;
    }
    public int compare (Object a, Object b) {
        int[] int_a = (int[]) a;
        int[] int_b = (int[]) b;
        return (int_a[index] - int_b[index]);
    }
}