use std::io::*;

fn main() {
    let mut input: String = String::new();
    std::io::stdin().read_to_string(&mut input).ok();
    let mut itr = input.trim().split_whitespace();
    let mut s: Vec<char> = itr.next().unwrap().chars().rev().collect();
    s.push('0');
    let n = s.len();
    s.push('0');

    let mut ans = 0;
    let mut carry = 0;
    for i in 0..n {
        if s[i] == '0' {
            if carry == 1 {
                s[i] = '1';
                carry = 0;
            } else {
            continue;
            }
        }

        if carry == 0 {
            ans += 1;
            if s[i+1] == '1' {
                carry = 1;
            }
        }
    }
    println!("{}", ans);
}