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 Pascal (FPC 3.0.4) (judge verdict: Accepted)

program main;
var 
   a : integer;
begin
    readln(a);
    if a < 1000 then 
        writeln(1000-a)
    else 
        begin 
            while ( a > 1000 ) do
                dec(a,1000);
            if a = 0 then 
                writeln('0')
            else
                writeln(1000-a);
        end;
end.