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

int main(){
    string c;
    cin>>c;
    int n=c.size(),ans=0;
    if(c[0]=='0'){cout<<0<<endl; return 0;}
    for(int i=1; i<n; ++i){
        if(c[i]!='0')ans++;
    }
    cout<<ans<<endl;
}