using System;
using System.Linq;
using System.Collections.Generic;

namespace test20190423
{
    class Program
    {
        static void Main(string[] args)
        {
            var ss = Console.ReadLine().Split(new string[] { " " }, StringSplitOptions.RemoveEmptyEntries).Select(x => long.Parse(x)).ToArray();
            long sum = 0;
            for (; ;)
            {
                ss[0] -= ss[1];
                if (ss[0] - ss[1] <= 0) break;
                ss[0] -= ss[1];
                sum += ss[1];
            }
            Console.WriteLine(sum);
            Console.ReadLine();
        }
    }
}