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: Wrong Answer)

using System;
using System.IO;
using System.Linq;
using System.Collections.Generic;

namespace CSharp_Shell
{

    public static class Program 
    {
        public static void Main() 
        {
        	int N = int.Parse(Console.ReadLine());
        	int b = 10;
        	for(int i=1; N>=i*1000; i++)
        	{
        		if(1000*i==N){b=0;}
        		else {b = 1000*(i+1) - N;}
        	}
        	Console.WriteLine(b);
        }
    }
}