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();
    I[] a=new I[n];
    for(int i=0;i<n;i++){
      a[i]=new I(sc.nextInt(),sc.nextInt());
    }
    Arrays.sort(a,(s1,s2)->s1.p-s2.p);
//    System.out.println(Arrays.toString(a));
    long k=0;
    long c=0;
    for(int i=0;i<n;i++){
//      System.out.println(a[i]);
      if(a[i].k+k>=m){
        c+=(m-k)*a[i].p;
        break;
      }else{
        k+=a[i].k;
        c+=(long)(a[i].k)*(long)(a[i].p);
      }
//      System.out.println("k"+k+" c"+c);
    }
    System.out.println(c);
  }
  static class I{
    int p;
    int k;
    I(int p,int k){
      this.p=p;
      this.k=k;
    }
    public String toString(){
      return String.valueOf(p)+":"+String.valueOf(k);
    }
  }
}