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: Wrong Answer)

program main;
var N , a , b ,c , final , initial , k ,amount:integer;
  begin
     readln(N);
     amount:=N;
     initial:=1000;
     k:=1;
     while initial<amount do
     begin
     k:=k+1;
     initial:=initial*k;
     end;
     
     final:=initial-amount;
     writeln(final);
     end.