#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <cmath>
using namespace std;

int main() {
    char s[101];
    cin >> s;

    int r = 0;
    for (int i = 0;; i++) {
        int c = s[i];
        if (c == 0) break;
        r += c - '0';
    }

    cout << r << endl;

    return 0;
}