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.Map;
import java.util.Map.Entry;
import java.util.Scanner;
import java.util.TreeMap;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int tempo = sc.nextInt();
		int max = sc.nextInt();
		long amount = 0;
		Map<Long, Long> map = new TreeMap<>();
		for (int i = 0; i < tempo; i++) {
			long key = sc.nextInt();
			long value = sc.nextInt();
			if (map.containsKey(key)) {
				map.put(key, map.get(key) + value);
			} else {
				map.put(key, value);
			}
		}
		for (Entry<Long, Long> entry : map.entrySet()) {
			if (max <= entry.getValue()) {
				amount += max * entry.getKey();
				break;
			} else {
				amount += entry.getKey() * entry.getValue();
				max -= entry.getValue();
			}
		}
		System.out.println(amount);
		sc.close();
	}
}