#include <algorithm>
#include <array>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <vector>
using namespace std;
#define int long long

constexpr int ctoi(int c) { return '0' <= c && c <= '9' ? c - '0' : -1; }

signed main() {
    cin.tie(0);
    ios::sync_with_stdio(0);

    string s;
    cin >> s;

    int ans = 0;
    for (auto &&i : s) {
        ans += ctoi(i);
    }

    cout << ans << "\n";
}