using System;

public class Hello
{
    static void Main()
    {
        string[] line = Console.ReadLine().Trim().Split(' ');
        var a = int.Parse(line[0]);
        var b = int.Parse(line[1]);
        var ans = a % b;
        if (ans < 0) ans += b > 0 ? b : -b;
        Console.WriteLine(ans);
    }
}