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>
using namespace std;

int main()
{
  long long N,M,ans=0;scanf("%lld %lld",&N,&M);
  priority_queue<pair<int,int>> AB;
  for(int A,B,i=0;i<N;i++)
  {
    scanf("%d %d",&A,&B);
    AB.push(make_pair(0-A,0-B));
  }
  while(M!=0)
  {
    long long A=0-AB.top().first,B=0-AB.top().second;
    AB.pop();
    if(M-B<0)ans+=A*M,M=0;
    else ans+=A*B,M-=B;
  }
  printf("%lld",ans);
}