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 <stdio.h>

#include <map>
using namespace std;
 
int main( void )
{
	int N,M ;
	scanf("%d %d", &N, &M ) ;
	map<int,int> o;
	for( int n = 0 ; n < N ; n++ ) {
		int a, b ;
		scanf("%d %d", &a, &b) ;
		o[a]+=b;
	}
	long long p=0;
	for( const auto & v : o ) {
		long long n = min( M, v.second ) ;
		p += n * v.first ;
		M -= n ;
		if( M <= 0 ) break ;
	}
	printf("%ld\n", p ) ;
	return 0 ;
}