#include<iostream>
using namespace std;
string fz(string s){
	int i = s.length();
	if(s[0] != '0'){
		return "0";
	}
	while(true){
		if(i == 0){
			return "0";
		}
		if(s[i - 1] == '0'){
			break;
		}
		i--;
	}
	for(int j = 0; j < i; j++){
		if(s[j] == '0'){
			s[j] = '1';
		}else{
			s[j] = '0';
	    }
	}
	return s;
} 
int main(){
	int i = 0;
	string s;
	cin>>s;
	int len = s.length();
.	while(true){
		if(fz(s) == "0"){
			cout<<i;
			return 0;
		}
		s = fz(s);
		i++;
	}	
	return 0;
}