import java.io.*;

public class Sum {
	public static void main (String[] args) throws IOException{
		try (BufferedReader in = new BufferedReader(new InputStreamReader(System.in))){
			
			String numString = new String(in.readLine());
			in.close();
			
			String[] array = numString.split("");
			 int sum = 0;
			 
			 for (int i = 0; i < numString.length(); i++){
			 	sum += Integer.parseInt(array[i]);
			 }
			 
			 System.out.println(sum);
			
		} catch (IOException e){
			// 例外
		}
	}
}