#include<bits/stdc++.h>

using namespace std;

int dlzka(long long d){
    for(long long i=0; i<45; i++){
        if(((1LL<<i)&d) ==0)
            return i;
    }
}



int main(){

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




    long long d = 0;
    for(int i=s.length()-1; i>=0; i--){
        d*=2;
        if(s[i]=='1')
            d+=1;
    }


    int pocet = 0;
    for(int i=1; i<=7; i++){
        int pos = dlzka(d);
        long long najd = d;
        if(pos>=s.length())
            break;

        for(int posun=1; posun<=pos; posun++){
            long long dd = (d << posun) | d;
            //cout<<"posun "<<posun<<" dlzka "<<dlzka(dd)<<endl;
            if(dlzka(dd)>=dlzka(najd))
                najd=dd;
        }
        d = najd;
        //cout<<dlzka(d)<<endl;
        /*
        for(int j=0; j<30; j++){
            cout<<(((1<<j) & d) !=0);
        }
        cout<<endl;
        */

        pocet++;



    }
    cout<<pocet<<endl;

}