Problem:
Score : 100 points

Problem Statement

We will buy a product for N yen (the currency of Japan) at a shop.

If we use only 1000-yen bills to pay the price, how much change will we receive?

Assume we use the minimum number of bills required.

Constraints

1 \leq N \leq 10000

N is an integer.

Input

Input is given from Standard Input in the following format:

N

Output

Print the amount of change as an integer.

Sample Input 1

1900

Sample Output 1

100

We will use two 1000-yen bills to pay the price and receive 100 yen in change.

Sample Input 2

3000

Sample Output 2

0

We can pay the exact price.

Solution in C# (.NET Core 3.1.201) (judge verdict: Accepted)

using System;
using System.Linq;
using System.Runtime.InteropServices.ComTypes;

namespace Tutorial
{
    class Program
    {
        static void Main(string[] args)
        {
            string input = Console.ReadLine();
            decimal inp = decimal.Parse(input);

            Console.WriteLine(Math.Ceiling(inp / 1000)*1000 - inp);


        }
    }
}