#include<bits/stdc++.h>
using namespace std;
#define ALL(x) x.begin(),x.end()
#define rep(i,n) for(int i=0;i<(n);i++)
#define debug(v) cout<<#v<<":";for(auto x:v){cout<<x<<' ';}cout<<endl;
#define INF 1000000000
#define mod 1000000007
using ll=long long;
const ll LINF=1001002003004005006ll;
int dx[]={1,0,-1,0};
int dy[]={0,1,0,-1};
ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
template<class T>bool chmax(T &a,const T &b){if(a<b){a=b;return true;}return false;}
template<class T>bool chmin(T &a,const T &b){if(b<a){a=b;return true;}return false;}

signed main(){
    cin.tie(0);
    ios::sync_with_stdio(0);

    string s;cin>>s;
    reverse(ALL(s));
    s.push_back('0');
    int n=(int)s.size();

    int nxt[n];//nxt0
    nxt[n-1]=n-1;
    for(int i=n-2;i>=0;i--){
        nxt[i]=nxt[i+1];
        if(s[i]=='0') nxt[i]=i;
    }

    ll dp1[n+1],dp2[n+1];
    rep(i,n+1)dp1[i]=LINF,dp2[i]=LINF;
    dp1[0]=0,dp2[0]=0;
    
    rep(i,n){
        if(s[i]=='0'){
            chmin(dp1[i+1],dp1[i]);
            chmin(dp1[i+1],dp2[i+1]+1);
            chmin(dp2[i+1],dp2[i]+1);
        }else{
            chmin(dp2[nxt[i]+1],dp1[i]+1);
            chmin(dp2[nxt[i]+1],dp2[i]+1);
            chmin(dp1[i+1],dp1[i]+1);
        }
    }
    // cout<<"   ";for(auto c:s) cout<<c<<"  ";cout<<endl;
    // rep(i,n+1){if(dp1[i]==LINF)cout<<"I";else cout<<dp1[i];cout<<"  ";}cout<<endl;
    // rep(i,n+1){if(dp2[i]==LINF)cout<<"I";else cout<<dp2[i];cout<<"  ";}cout<<endl;
    cout<<dp1[n]<<endl;
    return 0;
}