#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <iomanip>
#include <stack>
#include <algorithm>
#include <string>
#include <map>
#include <iterator>
#include <set>
#include <queue>

using namespace std;

int main() {

    string S;
    cin >> S;
    int N = S.size();
    int cnt0 = 0;
    for (int i = 0; i < N; ++i) {
        if (S[i] == '0') {
            cnt0 += 1;
        }
    }

    cout << N - 1 - cnt0 << endl;
    return 0;
}