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{
    void solve(){
        Scanner scan = new Scanner(System.in);
        int n = scan.nextInt();
        int m = scan.nextInt();
        Store[] s = new Store[n];
        for(int i = 0; i < n; i++){
            s[i] = new Store(scan.nextInt(), scan.nextInt());
        }
        Arrays.sort(s);
        long out = 0;
        int i = 0;
        for(i = 0; m > 0; i++){
            for(int j = 0; j < s[i].count && m > 0; j++){
                m--;
                out += s[i].price;
            }
        }
        System.out.println(out);
    }

    public class Store implements Comparable<Store>{
        int price, count;
        public Store(int price, int count){
            this.price = price;
            this.count = count;
        }

        @Override
        public int compareTo(Store s) {
            if(this.price == s.price) return Integer.compare(s.count, this.count);
            return Integer.compare(this.price, s.price);
        }
    }

    public static void main(String[] args){
        new Main().solve();
    }
}