Bulbs

#include<bits/stdc++.h>
using namespace std;

int n;

void n2(int& ans,string& s)
{
    if(s[0]=='1' && s[1]=='1')
    {
        ans+=2;
        s[0]='0',s[1]='0';
    }
    else if(s[0]=='1' && s[1]=='0')
    {
        ans+=3;
        s[0]='0';
    }
    else if(s[0]=='0' && s[1]=='1')
    {
        ans+=1;
        s[1]='0';
    }
}

void func(int ind, string& s, bool flip, int& ans,int pos)
{
    if(ind==(n-3))
    {
        if(s[ind]=='1' && s[ind+1]=='1' && s[ind+2]=='1')
        {
            if(!flip)
            {
                ans+=5;
                s[ind]='0',s[ind+1]='0',s[ind+2]='0';
            }
            else
            {
                ans+=2;
                s[ind]='1',s[ind+1]='0',s[ind+2]='0';
            }
        }
        else if(s[ind]=='1' && s[ind+1]=='1' && s[ind+2]=='0')
        {
            if(!flip)
            {
                ans+=4;
                s[ind]='0',s[ind+1]='0',s[ind+2]='0';
            }
            else
            {
                ans+=3;
                s[ind]='1',s[ind+1]='0',s[ind+2]='0';
            }
        }
        else if(s[ind]=='1' && s[ind+1]=='0' && s[ind+2]=='1')
        {
            if(!flip)
            {
                ans+=4;
                s[ind]='0',s[ind+1]='0',s[ind+2]='0';
            }
            else
            {
                ans+=3;
                s[ind]='1',s[ind+1]='0',s[ind+2]='0';
            }
        }
        else if(s[ind]=='1' && s[ind+1]=='0' && s[ind+2]=='0')
        {
            if(!flip)
            {
                ans+=7;
                s[ind]='0',s[ind+1]='0',s[ind+2]='0';
            }
            else
            {
                ans+=0;
                s[ind]='1',s[ind+1]='0',s[ind+2]='0';
            }
        }
        else if(s[ind]=='0' && s[ind+1]=='1' && s[ind+2]=='1')
        {
            if(!flip)
            {
                ans+=2;
                s[ind]='0',s[ind+1]='0',s[ind+2]='0';
            }
            else
            {
                ans+=5;
                s[ind]='1',s[ind+1]='0',s[ind+2]='0';
            }
        }
        else if(s[ind]=='0' && s[ind+1]=='1' && s[ind+2]=='0')
        {
            if(!flip)
            {
                ans+=3;
                s[ind]='0',s[ind+1]='0',s[ind+2]='0';
            }
            else
            {
                ans+=4;
                s[ind]='1',s[ind+1]='0',s[ind+2]='0';
            }
        }
        else if(s[ind]=='0' && s[ind+1]=='0' && s[ind+2]=='1')
        {
            if(!flip)
            {
                ans+=1;
                s[ind]='0',s[ind+1]='0',s[ind+2]='0';
            }
            else
            {
                ans+=6;
                s[ind]='1',s[ind+1]='0',s[ind+2]='0';
            }
        }
        else
        {
            if(!flip)
            {
                ans+=0;
                s[ind]='0',s[ind+1]='0',s[ind+2]='0';
            }
            else
            {
                ans+=7;
                s[ind]='1',s[ind+1]='0',s[ind+2]='0';
            }
        }

        return;
    }

    if(flip)
    {
        ans+=1;
        if((pos+1 == ind+1) && (ind+1 != n-3))
        {
            if(s[ind+1]=='1')
                func(ind+1,s,false,ans,pos);
            else
            {
                func(ind+1,s,true,ans,pos);
                s[ind+1]='1';
            }
        }
        else if((pos+1 == ind+1) && (ind+1 == n-3))
            func(ind+1,s,true,ans,pos);
        else
        {
            func(ind+1,s,false,ans,pos);
            s[ind+1]='0';
        }
    }
    else
    {
        if(ind+1 == n-3)
            func(ind+1,s,false,ans,pos);
        else
        {
            if(s[ind+1]=='1')
            {
                func(ind+1,s,true,ans,pos);
                s[ind+1]='0';
            }
            else
                func(ind+1,s,false,ans,pos);
        }
    }
    return;
}

main()
{
    string s;cin>>s;
    n=s.length();int ans=0;

    if(n==1)
    {
        if(s[0]=='1')
            ans++;
        cout<<ans<<endl;
    }
    else if(n==2)
    {
        n2(ans,s);
        cout<<ans<<endl;
    }
    else
    {
        for(int i=0;i<n-2;i++)
        {
            if(i==(n-3) && s[i]=='1')
            {
                func(i,s,false,ans,i);
                s[i]='0';
            }
            if(s[i]=='1')
            {
                func(i,s,true,ans,i);
                s[i]='0';
            }
             cerr<<s<<endl;
             cerr<<"ans: "<<ans<<endl;
        }
        cout<<ans<<endl;
    }
    return 0;
}