import java.io.*; import java.util.*; import java.util.stream.*; public class Main { public static void main(String[] args) throws Exception { Scanner sc = new Scanner(); char[] inputs = sc.next().toCharArray(); int length = inputs.length; int[][] dp = new int[length][2]; if (inputs[length - 1] == '0') { dp[length - 1][1] = 2; } else { dp[length - 1][0] = 1; dp[length - 1][1] = 1; } for (int i = length - 2; i >= 0; i--) { if (inputs[i] == '0') { dp[i][0] = Math.min(dp[i + 1][0], dp[i + 1][1] + 1); dp[i][1] = Math.min(dp[i + 1][0] + 2, dp[i + 1][1] + 1); } else { dp[i][0] = Math.min(dp[i + 1][0] + 1, dp[i + 1][1] + 2); dp[i][1] = Math.min(dp[i + 1][0] + 1, dp[i + 1][1]); } } System.out.println(Math.min(dp[0][0], dp[0][1] + 1)); } } class Utilities { static String arrayToLineString(Object[] arr) { return Arrays.stream(arr).map(x -> x.toString()).collect(Collectors.joining("\n")); } static String arrayToLineString(int[] arr) { return String.join("\n", Arrays.stream(arr).mapToObj(String::valueOf).toArray(String[]::new)); } } class Scanner { BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); StringTokenizer st = new StringTokenizer(""); StringBuilder sb = new StringBuilder(); public Scanner() throws Exception { } public int nextInt() throws Exception { return Integer.parseInt(next()); } public long nextLong() throws Exception { return Long.parseLong(next()); } public double nextDouble() throws Exception { return Double.parseDouble(next()); } public int[] nextIntArray() throws Exception { return Stream.of(br.readLine().split(" ")).mapToInt(Integer::parseInt).toArray(); } public String next() throws Exception { while (!st.hasMoreTokens()) { st = new StringTokenizer(br.readLine()); } return st.nextToken(); } }