#include<iostream>
#include<string>
#include<iomanip>
#include<cmath>
#include<vector>
#include<algorithm>

using namespace std;

#define int long long
#define endl "\n"

const long long INF = (long long)1e18;
const long long MOD = 1'000'000'007; 

string yn(bool f){return f?"Yes":"No";}
string YN(bool f){return f?"YES":"NO";}



signed main(){
	// cin.tie(0);
	// ios::sync_with_stdio(false);
	// cout<<fixed<<setprecision(10);
	
	string N;
	vector<int> con;
	vector<vector<int>> dp;
	
	cin>>N;
	
	N = "0" + N;
	
	con.resize(N.size()+2, 0);
	for(int i = N.size()-1; i >= 0; i--){
		if(i == N.size()-1){
		} else {
			if(N[i] != N[i+1]){
				con[i] = 0;
			} else {
				con[i] = con[i+1] + 1;
			}
		}
	}
	// for(int i = 0; i < N.size(); i++){
		// cout<<"i = "<<i<<" con = "<<con[i]<<endl;
	// }
	// cout<<"D"<<endl;	
	// cout<<"A"<<endl;
	dp.assign(N.size()+10, vector<int>(2, INF));
	// cout<<"B"<<endl;
	dp[0][0] = 0;
	// cout<<"C"<<endl;
	for(int i = N.size()-1, j = 0; i >= 0; i--, j++){
		// cout<<i<<" N = "<<N[i]<<endl;
		if(N[i] == '0'){
			dp[j+1][0] = min(dp[j+1][0],min(dp[j][0], dp[j][1]+1));
			dp[j+1][1] = min(dp[j+1][1],min(dp[j][0]+1, dp[j][1]+1));
		} else if(N[i] == '1'){
			// dp[j][0]+1;
			// dp[j][1];
			// dp[j+con[i]+1][1];
			// cout<<"con = "<<con[i]<<" j = "<<j<<endl;
			// = min(dp[j][0]+1, dp[j][1]);
			// dp[j+con[i]+1][1] = min(dp[j+con[i]+1][1],min(dp[j][0]+1, dp[j][1]));
			dp[j+1][0] = min(dp[j+1][0],dp[j][0] + 1);
			dp[j+1][1] = min(dp[j+1][1],min(dp[j][1],dp[j][0]+1));
		}
		// cout<<"dp "<<dp[j][0]<<" "<<dp[j][1]<<endl;
		// cout<<i<<" <> "<<endl;
	}
	cout<<dp[N.size()][0]<<endl;
	
	// cout<<"E "<<endl;
	return 0;
}