#include<bits/stdc++.h>

using namespace std;

int main(){

    string s;
    cin>>s;
    if(s[0]=='0'){
        cout<<"-1"<<endl;
        return 0;
    }

    int pocet=0;
    for(int i=0; i<s.length(); i++){
        if(s[i]=='0'){
            string t = s;
            int posun = i;
            //cout<<posun<<endl;
            for(int j=0; j<s.length()-posun; j++){
                s[j+posun] = (t[j]=='1' || s[j+posun]=='1' ? '1' : '0');
            }
            pocet++;
        }
        //cout<<s<<endl;

    }
    cout<<pocet<<endl;

}