using System;
using System.Linq;

public class yukicoder{
    public static void Main(){
        string[] input = Console.ReadLine().Trim().Split(' ');
        int length = int.Parse(input[0]);
        int eat = int.Parse(input[1]);
        int a = 0;
        int b = 0;
        
        while(true)
        {
            length = length - eat;
            a = a + eat;
            if(length - eat <= 0)
            {
                break;                
            }
            length = length - eat;
            b = b + eat;
        }
        
        Console.WriteLine(b);

    }
}