H. Steaks
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output

Motasem wants to cook n steaks (the steak consists of two faces) for his friends, and each face of the steak needs to be cooked for 5 minutes. Unfortunately, his pans can only fit 2 steaks at a time, and he only has k pans. If Motasem is cooking his steaks optimally, what is the minimum number of minutes he needs to cook all n steaks?

Input

A single line containing two space separated integers $$$n,k$$$ ($$$1\le n,k \le 10^9$$$) represent the number of steaks and pans respectively.

Output

A single integer represents the minimum time needed to cook all steaks

Example
Input
3 1
Output
15