Competitions

# Toasts

You want to roast a few toasts for the upcoming party. There is a frying pan, that can roast at the same time k toasts. Roasting the toast from one side takes 2 minutes. We assume that placing a toast into a frying pan, turning and removing it from the pan performed instantly. Write a program that computes the minimum time in minutes for roasting n toasts. Toasts should not be removed from the pan sooner or later that 2 minutes required for toasting one side. Each toast should be roasted from both sides.

#### Input

The first line contains two integers n and k (0n1000, 1k50) - the number of toasts and pan capacity.

#### Output

Print the minimum time in minutes required to roast n toasts.

Time limit 1 second
Memory limit 128 MiB
Input example #1
3 2

Output example #1
6