Banana Pricing: Buy 1 Get 1 Free

You are given the number of bananas and the price per banana. Due to a special offer, every two bananas are sold at the price of one. In other words, for every pair of bananas, you only pay once. If there is an odd banana out, you pay the full price for it.

Your task is to compute the total cost.

inputFormat

The input consists of a single line containing two space-separated integers:

• quantity: the number of bananas.
• price_per_banana: the price for one banana.

You may assume that the numbers provided are non-negative integers.

outputFormat

Output a single integer representing the total cost calculated by applying the 'Buy 1 Get 1 Free' offer.

4 3

6