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Problems

Toasts

Toasts

Time limit 1 second
Memory limit 128 MiB

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 data

The first line contains two integers n and k\:(0 \le n \le 1000, 1 \le k \le 50) — the number of toasts and pan capacity.

Output data

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

Examples

Input example #1
3 2
Output example #1
6