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.Arrays;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) throws Exception {

//    	File file = new File("test.txt");
//    	Scanner sc = new Scanner(file);
    	Scanner sc = new Scanner(System.in);
    	int N = sc.nextInt();
    	int M = sc.nextInt();
    	long[][] A = new long[N][2];
    	for(int i = 0; i < N; i++){
    		A[i][0] = sc.nextLong();
    		A[i][1] = sc.nextLong();
    	}
    	sc.close();
    	Arrays.sort(A, (s, t) -> Long.compare(s[0],t[0]));
    	long ans = 0;
    	int sum = 0;
    	for(int i = 0; i < N; i++){
    		if(sum + A[i][1] <= M){
    			ans += A[i][0] * A[i][1];
    			sum += A[i][1];
    		}else if(sum < M){
    			ans += (M - sum) * A[i][0];
    			sum += M - sum;
    		}
    	}
    	System.out.println(ans);
    }
}