#include <bits/stdc++.h>

using namespace std;

using ll = long long;

constexpr char newl = '\n';

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    string s;
    cin >> s;

    int ans = 0;
    for (int i = 0; i + 1 < s.size(); i++) {
        if (s[0] != '0' && s[i + 1] != '0') ++ans;
    }
    cout << ans << newl;

    return 0;
}