#include <bits/stdc++.h>
using namespace std;

int main(){
	int n,g,s,b,q;
	cin>>n;
	q = n / 1000;
	b = n / 100 % 10;
	s = n / 10 % 10;
	g = n % 10;
	cout<<q+b+s+g<<endl;
    return 0;
}

/**************************************************************
	Problem: 1390
	User: admin
	Language: C++
	Result: Accepted
	Time:17 ms
	Memory:2072 kb
****************************************************************/