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;
typedef long long ll;
typedef pair <ll, ll> pii;

const ll D = 100007;

pii a[D];

int main()
{
    ll n, m, ans = 0;
    cin >> n >> m;
    for (ll i = 1; i <= n; i++)
        cin >> a[i].fi >> a[i].se;
    sort(a + 1, a + n + 1);

    for (ll i = 1; i <= n; i++)
        ans += min(a[i].se, m) * a[i].fi, m -= min(a[i].se, m);
    cout << ans << endl;
}