// Missing a space
#include <bits/stdc++.h>
#define rep(i, n) for(int i=0; i<(int)(n); ++i)
using namespace std;
using ll = long long;
using ull = unsigned long long;

int main(){
    string C;
    cin >> C;
    int cnt = 0;
    for(ll i=0; i<C.size(); ++i){
        if(C[i] == '0') ++cnt;
    }
    ll ans = C.size()-cnt-1;
    cout << ans << endl;
    return 0;
}