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();
    
    Long[][] AB = new Long[N][2];

    for (int i = 0; i < N; i++) {
      AB[i][0] = sc.nextLong();
      AB[i][1] = sc.nextLong();
    }

    sc.close();

    Arrays.sort(AB, (a, b) -> Long.compare(a[0], b[0]));
    
    long sum = 0;

    int i = 0;

    while (0 < M) {
      if (AB[i][1] < M){
        sum += AB[i][0] * AB[i][1];
        M -= AB[i][1];
      } else {
        sum += AB[i][0] * M;
        M = 0;
      }
      i++;
    }

    System.out.println(sum);

  }

}