fn make_list(sep: &str) -> String {
    let mut counter = 0;
    let mut make_item = |label| {
        counter += 1;
        format!("{}{}{}", counter, sep, label)
    };
    format!(
        "{}\n{}\n{}",
        make_item("First"),
        make_item("Second"),
        make_item("Third")
    )
}

fn main() {
    println!("{}", make_list(". "))
}