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.Collections.Generic;
using System.Linq;

public class Hello
{
    public static void Main()
    {
        hoge();
        //System.Console.ReadLine();
    }

    public static void hoge()
    {
        var n = int.Parse(System.Console.ReadLine());

        var ans = 0;

        for(int i = 1; i <= 10; i++)
        {
            if(1000 * i - n < 1000 && 1000 * i - n >= 0)
            {
                ans = 1000 * i - n;
                break;
            }
        }

        System.Console.WriteLine(ans);

    }
}