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 PYTHON):

Solution:
N,M=map(int, raw_input().split())
e_list=[]
result=0
m=M

for i in range(N):
    e_list.append(map(int, raw_input().split()))

e_list.sort()

#print N,M,e_list

for i in range(N):
    cost=e_list[i][0]
    mnum=e_list[i][1]
#    print cost,mnum,":",m
    if m == 0:
#        print result
        break
    elif m >= mnum:
        result = result + cost * mnum
        m = m - mnum
    elif m < mnum:
        result = result + cost * m
        m = 0

print result