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 N,i,x,y:integer;
begin
    readln(N);
    i:=0; x:=1000; y:=1;
    if N mod 1000 = 0 then writeln('0')
    else begin
    while x<N do begin
    y:=y+1; x:=x+1000;
    end;
    writeln(y*1000-N);
end;
end.