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

int main() {
    string c;
    cin >> c;

    int r = 0;

    for (auto& i : c) {
        r += i != '0';
    }

    cout << r - 1 << endl;

    return 0;
}