import java.util.*;
 
class Main {
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    if (N%1000 == 0){
      System.out.println(0);
    }else if (N<=1000&&0<N){
      System.out.println(1000-N);
    }else if(1000<N&&N<10000){
      System.out.println(1000-N%1000);
    }
  }
} import java.util.*; util.* java class Main {
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    if (N%1000 == 0){
      System.out.println(0);
    }else if (N<=1000&&0<N){
      System.out.println(1000-N);
    }else if(1000<N&&N<10000){
      System.out.println(1000-N%1000);
    }
  }
} Main public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    if (N%1000 == 0){
      System.out.println(0);
    }else if (N<=1000&&0<N){
      System.out.println(1000-N);
    }else if(1000<N&&N<10000){
      System.out.println(1000-N%1000);
    }
  } main {
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    if (N%1000 == 0){
      System.out.println(0);
    }else if (N<=1000&&0<N){
      System.out.println(1000-N);
    }else if(1000<N&&N<10000){
      System.out.println(1000-N%1000);
    }
  } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int N = sc.nextInt(); N sc.nextInt() sc.nextInt sc if (N%1000 == 0){
      System.out.println(0);
    }else if (N<=1000&&0<N){
      System.out.println(1000-N);
    }else if(1000<N&&N<10000){
      System.out.println(1000-N%1000);
    } N%1000 == 0 N%1000 N 1000 0 {
      System.out.println(0);
    } System.out.println(0) System.out.println System.out System System.out 0 if (N<=1000&&0<N){
      System.out.println(1000-N);
    }else if(1000<N&&N<10000){
      System.out.println(1000-N%1000);
    } N<=1000&&0<N N<=1000 N 1000 0<N 0 N {
      System.out.println(1000-N);
    } System.out.println(1000-N) System.out.println System.out System System.out 1000-N 1000 N if(1000<N&&N<10000){
      System.out.println(1000-N%1000);
    } 1000<N&&N<10000 1000<N 1000 N N<10000 N 10000 {
      System.out.println(1000-N%1000);
    } System.out.println(1000-N%1000) System.out.println System.out System System.out 1000-N%1000 1000 N%1000 N 1000 String[] args args
import java.util.*;
 
class Main {
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    if (N%1000 == 0){
      System.out.println(0);
    }else if (N<=1000&&0<N){
      System.out.println(1000-N);
    }else if(1000<N&&N<10000){
      System.out.println(1000-N%1000);
    }
  }
}
