# include <bits/stdc++.h>
using namespace std;
constexpr int ctoi(const char c) { return ('0' <= c && c <= '9') ? (c - '0') : -1; }
int main() {
    string s;
    cin >> s;
    int sum = 0;
    for (auto& c : s) {
        sum += ctoi(c);
    }
    cout << sum << endl;
}