fn main() {
    let mut buf = String::new();

    std::io::stdin().read_line(&mut buf).unwrap();

    if buf.chars().nth(0).unwrap() != '1' || buf.len() == 1 {
        println!("-1");
        return;
    }
    
    let mut n = 0;

    for c in buf.trim().chars().skip(1) {
        if c != '3' {
            println!("-1");
            return;
        }
        n += 1;
    }
    println!("{}", n);
}