using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine(rest(1000.1111f, 1006.3233f));

    }

    static double rest(float a, float b)

    {float res=a*b;

    for (int i=0; i<999999999; i++)

     if (i<=res && i+1>res) {res = res-i; break;}

    return res;

    }

}