#include<bits/stdc++.h> 
using namespace std;
	int main(){
	int n=0,x,g,s,b,q;
	cin>>x;
	g=x%10;
	s=x/10%10;
	b=x/100%10;
	q=x/1000;
	n=g+s+b+q;
	cout<<n;
	
	
	
	
	
	
	
	
	
	
	
		return 0;
	}
/**************************************************************
	Problem: 1390
	User: zhangchenhao
	Language: C++
	Result: Accepted
	Time:17 ms
	Memory:2072 kb
****************************************************************/