To encourage customers to shop more, some stores charge lower prices if you buy multiples of an item. For example, if you buy one, it may cost you $5 but if you buy two, it will cost you $8 instead of $10.
Let’s assume a store provides discounts as follows:
1. No discount if you buy only one.
2. $2 discount for each additional item if you buy more than one. Given the number of items a customer has purchased and the price for one item, you are to compute the total cost for the customer.
There is one input line, it provides two integers: the first integer c (1 ≤ c ≤ 100) is the number of items purchased by the customer, and the second integer p (3 ≤ p ≤ 50) is the price for one item.
Print the total cost for the customer on a line by itself with no leading or trailing spaces.