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.*;

class Main{
  public static void main (String[] args){
    Scanner sc = new Scanner (System.in);
    int N = sc.nextInt();
    int M = sc.nextInt();
    long ans = 0;
    long array[][] = new long[N][2];
    for (int i=0;i<N;i++){
      array[i][0] = sc.nextLong();
      array[i][1] = sc.nextLong();
    }
    Arrays.sort(array,(x,y)->Long.compare(x[0], y[0]));
    for (int i=0;i<N;i++){
      if (M>=array[i][1]){
        //買占め
        ans += array[i][0]*array[i][1];
        M -= array[i][1];
      }else{
        ans += array[i][0]*M;
        break;
      }
    }
    System.out.println(ans);
  }
}