fn starts_with_ignoring_case(s: &str, prefix: &str) -> bool {
    let s = s.chars().flat_map(char::to_lowercase);
    let mut prefix = prefix.chars().flat_map(char::to_lowercase);
    
    for (a, b) in s.zip(prefix.by_ref()) {
        if a != b { return false; }
    }
    
    prefix.next().is_none()
}