Problem Statement

AtCoder Inc. sells merchandise through its online shop.
Takahashi has decided to purchase N types of products from there.
For each integer i from 1 to N, the i-th type of product has a price of P_i yen each, and he will buy Q_i of this.
Additionally, he must pay a shipping fee.
The shipping fee is 0 yen if the total price of the products purchased is S yen or above, and K yen otherwise.
He will pay the total price of the products purchased plus the shipping fee.
Calculate the amount he will pay.

Input

The input is given from Standard Input in the following format:
N S K
P_1 Q_1
P_2 Q_2
$\vdots$
P_N Q_N

Output

Print the amount Takahashi will pay for online shopping.

Constraints

• $1\leq N\leq 100$
• $1\leq S\leq 10000$
• $1\leq K\leq 10000$
• $1\leq P_i\leq 10000$
• $1\leq Q_i\leq 100$
• All input values are integers.

Sample Input 1

2 2000 500
1000 1
100 6

Sample Output 1

2100

Takahashi buys one product for 1000 yen and six products for 100 yen each.
Thus, the total price of the products is $1000\times 1+100\times 6=1600$ yen.
Since the total amount for the products is less than 2000 yen, the shipping fee will be 500 yen.
Therefore, the amount Takahashi will pay is 1600+500=2100 yen.

Sample Input 2

3 2000 500
1000 1
100 6
5000 1

Sample Output 2

6600

The total price of the products is $1000\times 1+100\times 6+5000\times 1=6600$ yen.
Since the total amount for the products is not less than 2000 yen, the shipping fee will be 0 yen.
Therefore, the amount Takahashi will pay is 6600+0=6600 yen.

Sample Input 3

2 2000 500
1000 1
1000 1

Sample Output 3

2000

There may be multiple products with the same price per item.

见题面 Input 部分

见题面 Output 部分