#include<bits/stdc++.h>
using namespace std;
int main(){
	int x,g,s,b,q,h=0;
	scanf("%d",&x);
	g=x%10;
	s=x/10%10;
	b=x/100%10;
	q=x/1000;
	h=g+s+b+q;
	printf("%d",h);
return 0;
}

/**************************************************************
	Problem: 1390
	User: fuhoubin
	Language: C++
	Result: Accepted
	Time:14 ms
	Memory:2076 kb
****************************************************************/