import java.util.Scanner;

public class Main {
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		String n = sc.next();
		sc.close();

		StringBuilder sb = new StringBuilder(n);
		sb.reverse().append("0");
		int ans = 0;
		boolean flg = false;
		for (int i = 0; i < n.length(); i++) {
			if (flg) {
				if (sb.charAt(i) == '0') {
					ans++;
					if (sb.charAt(i + 1) == '0') {
						flg = false;
					}
				}
			} else {
				if (sb.charAt(i) == '1') {
					ans++;
					if (sb.charAt(i + 1) == '1') {
						flg = true;
					}
				}
			}
		}
		if (flg) {
			ans++;
		}
		System.out.println(ans);
	}
}