#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const ll mod = 1e9 + 7;
const ll inf = (1 << 30) - 1;
const ll infll = (1LL << 61) - 1;

int a;

int main()
{
    string s;
    cin >> s;
    for (int i = 0; i < s.size(); i++)
    {
        a += s[i] - '0';
    }
    cout << a << endl;
}