#include <bits/stdc++.h>
using namespace std;
#define modulo 1000000007
#define mod(mod_x) ((((long long)mod_x+modulo))%modulo)
#define Inf 100000000



int main(){
	string S;
	cin>>S;
	
	reverse(S.begin(),S.end());
	int ans = 0;
	for(int i=0;i<S.size();i++){
		if(i==S.size()-1){
			if(S[i]=='1')ans++;
			continue;
		}
		
		if(S[i]=='0')continue;
		
		if(S[i+1]=='0'){
			ans++;
			continue;
		}
		
		int x = i;
		while(true){
			if(x==S.size()){
				S+='1';
				break;
			}
			if(S[x]=='0'){
				S[x]='1';
				break;
			}
			S[x]='0';
			x++;
		}
		ans++;
	}
	
	
	cout<<ans<<endl;
	
	
	return 0;
}