/*==========================================================================*/
/*
    auther:    Dev1ce
    created:   08.04.2024 21:18:22
*/
/*--------------------------------------------------------------------------*/

#include<bits/stdc++.h>

using namespace std;


int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	string s;
	cin >> s;
	int n = (int)s.size();
	int sum = 0;
	for (int i = 0; i < n; i++) {
		int a = s[i] - '0';
		sum += a;
	}
	cout << sum << '\n';
	return 0;
}