import java.util.*;
  public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        for(int i=0; i<=N; i++){
          int ans = 1000*i - N;
          if (ans >= 0){
            System.out.println(ans);
            break;
          } else if (ans < 0) {
            continue;
          }
        }
    }
  }
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz