#include <bits/stdc++.h>
using namespace std;
int main(){
    int x,s,g,v,b,m;
    scanf("%d",&x);
	g=x%10;
	v=x/10%10;
	b=x/100%10;
	m=x/1000;
	s=g+v+b+m;
	printf("%d",s); 	
}
/**************************************************************
	Problem: 1390
	User: tonghuawei
	Language: C++
	Result: Accepted
	Time:15 ms
	Memory:2076 kb
****************************************************************/