Cast

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Numerics;

namespace SomeNameSpace
{
    class Program
    {
        static void Main(string[] args)
        {
            var number = Console.ReadLine();


            var split = number.Split('.');


            var secondPart = "";

            if (split[1].Length<3)
            {
                secondPart = split[1];

                for (int i = split[1].Length; i < 3; i++)
                {
                    secondPart += "0";
                }

            }
            else
            {
                secondPart = split[1].Substring(0,3);
            }
            Console.WriteLine($"{split[0]}.{secondPart}");

        }
    }
}