import java.util.*;

public class Main {
    static char[] arr;
    static int[][] dp;
	public static void main (String[] args) {
    	Scanner sc = new Scanner(System.in);
    	arr = sc.next().toCharArray();
    	int length = arr.length;
    	dp = new int[length + 1][2];
    	for (int[] arr : dp) {
    	    Arrays.fill(arr, -1);
    	}
    	System.out.println(dfw(length, 0));
    }
    
    static int dfw(int idx, int added) {
        if (idx == 0) {
            return added;
        }
        if (dp[idx][added] == -1) {
            if (added == 0) {
                if (arr[idx - 1] == '0') {
                    dp[idx][added] = dfw(idx - 1, 0);
                } else {
                    dp[idx][added] = Math.min(dfw(idx - 1, 0), dfw(idx - 1, 1)) + 1;
                }
            } else {
                if (arr[idx - 1] == '0') {
                    dp[idx][added] = Math.min(dfw(idx - 1, 0), dfw(idx - 1, 1)) + 1;
                } else {
                    dp[idx][added] = dfw(idx - 1, 1);
                }
            }
        }
        return dp[idx][added];
    }
}