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 CPP):

Solution:
#include<bits/stdc++.h>
#define FI first
#define SE second
using namespace std;

long long a,b;
int n,m;
pair<long long,long long> arr[100005];
long long ans;

int main(){
	scanf("%d%d",&n,&m);
	for(int i =0;i<n;i++){
		scanf("%d%d",&a,&b);
		arr[i] = {a,b};
	}
	sort(arr,arr+n);
	for(int i = 0;i<n;i++){
		ans += arr[i].FI*(min((long long)m,arr[i].SE));
		m -= min((long long)m,arr[i].SE);
	}
	printf("%lld\n",ans);
	return 0;
}