#include <iostream>
#include <string>
#include <algorithm>

using namespace std;

string s;
int nx[200005];
int dp[200005][2];

int main(void)
{
	ios::sync_with_stdio(0);
	cin.tie(0);
	
	cin >> s;
	int n = s.size();
	reverse(s.begin(), s.end());
	s += "00";
	
	nx[n] = n+1;
	for(int i = n-1; i >= 0; i--){
		nx[i] = nx[i+1];
		if(s[i+1] == '0') nx[i] = i+1;
	}
	
	for(int i = 0; i <= n+1; i++){
		for(int j = 0; j < 2; j++){
			dp[i][j] = 1e9;
		}
	}
	dp[0][s[0]-'0'] = 0;
	
	for(int i = 0; i <= n; i++){
		dp[i+1][s[i+1]-'0'] = min(dp[i+1][s[i+1]-'0'], dp[i][0]);
		dp[i+1][s[i+1]-'0'] = min(dp[i+1][s[i+1]-'0'], dp[i][1] + 1);
		if(i < n) dp[nx[i]][1] = min(dp[nx[i]][1], dp[i][1] + 1);
	}
	
	/*for(int i = 0; i <= n+1; i++){
		for(int j = 0; j < 2; j++){
			cout << dp[i][j] << " ";
		}
		cout << endl;
	}*/
	
	cout << dp[n+1][0] << endl;
	
	return 0;
}