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>
#include <vector>


using namespace std;


int main(){

 int n,m;
 cin>>n>>m;

 vector<pair<int, int> >mp(n);


 for(int i=0;i<n;i++){
     cin>>mp[i].first>>mp[i].second;
 }

  sort(mp.begin(),mp.end());

  int64_t ans = 0, i = 0;

 while(m>0){

  ans += (int64_t)mp[i].first * min(mp[i].second,m);
  m -= mp[i].second;
  i++;
 }

 cout<<ans<<endl;

 return 0;
}