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 final int MOD=1000000007;

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int m = sc.nextInt();
        ArrayList<Long> a = new ArrayList<>();
        HashMap<Long,Long> energy = new HashMap<>();
        for(int i=0;i<n;i++){
            long tempA = sc.nextInt();
            long tempB = sc.nextInt();
            if(energy.containsKey(tempA)){
                energy.put(tempA,energy.get(tempA)+tempB);
            }else{
                energy.put(tempA,tempB);
                a.add(tempA);
            }
        }

        Collections.sort(a);

        long ans = 0;
        for(Long value:a){
            long count = energy.get(value);
            //System.out.println(value+" "+count);
            for(long i=0;i<count;i++){
                m--;
                ans+=value;
                if(m==0){
                    System.out.println(ans);
                    return;
                }
            }
        }

    }
}