import java.io.*;
import java.util.*;
import java.lang.*;

class Main{
  public static void main(String[] args) throws IOException{
    BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
    String n=br.readLine();

    int sum=0;
    for(int i=0;i<n.length();i++){
      int x=Character.getNumericValue(n.charAt(i));
      sum+=x;
    }

    System.out.println(sum);
  }
  }