#include<bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
#define endl "\n"
#define rep(i, a, n) for (int i = a; i < n; ++i)
#define all(x) (x).begin(), (x).end()

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    string c;
    cin >> c;

    ll ans = c.length() - 1;
    rep(i, 0, c.length()) {
        if (c[i] == '0') ans--;
    }
    cout << ans << endl;
    return 0;
}