#include<iostream>
#include<vector>
#include<string>
#include<algorithm>
#include<map>
#include<cmath>
#include<queue>
#include<stack>
#include<list>

#define endl "\n"
using namespace std;
using ll = long long;
const ll MOD = 1e9+7;
const ll INF = 1e18;
#define REP(i, n) for(int i = 0; i < n; i++)
using Graph = vector<vector<int>>;

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