#include <bits/stdc++.h>
#define rep(i, n) for (ll i = 0; i < n; ++i)
typedef long long ll;
using namespace std;
const int INF = 1e9;

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

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

    cout << ans << endl;

    return 0;
}