#include <algorithm>
#include <cmath>
#include <deque>
#include <iostream>
#include <queue>
#include <vector>
#define rep(i, a, n) for(int i = a; i < n; i++)
using namespace std;
using ll = long long;
using P = pair<int, int>;

int main()
{
    string s;
    cin >> s;
    int sum = 0;
    rep(i, 0, s.size()){
        int n = (s[i] - '0');
        sum += n;
    }
    cout << sum << endl;
    return 0;
}