import java.util.*;
import static java.lang.Math.*;

public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);

		// 入力
		String s = sc.next();

		// 計算
		int n = 0;
		
		for(int i = 0; i < s.length(); i++){
			int m = Integer.parseInt(s.substring(i, i+1));
			n = n + m;
		}

		// 出力
		System.out.println(n);

	}

}



/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