using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Net;
using System.IO;
namespace hi
{
    class prog
    {
        public static void Main(String []args)
        {
            string inp = Console.ReadLine();
            int a = Convert.ToInt32(inp.Split(' ')[0]);
            int b = Convert.ToInt32(inp.Split(' ')[1]);
            Console.WriteLine(Math.Abs(a) % Math.Abs(b));
        }
    }
}