use std::io::{self, BufRead, Write};

const ABC: [char; 26] = ['a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'];
const START: [char; 25] = ['a','b','c','d','e','f','g','h','i','j','k','l','m','o','p','q','r','s','t','u','v','w','x','y','z'];
const END: [char; 25] = ['b','c','d','e','f','g','h','i','j','k','l','m','o','p','q','r','s','t','u','v','w','x','y','z','a'];

fn get_lines() -> Vec<String> {
    let stdin = io::stdin();
    let lines: Vec<String> = stdin.lock().lines().map(|l| l.unwrap()).collect();
    return lines;
}

fn main(){
    let stdout = io::stdout();
    let mut bufout = io::BufWriter::new(stdout.lock());
    let s = &get_lines();
    let n = s[0].parse::<i32>().unwrap();
    if n == 1 {
        writeln!(bufout, "n").unwrap();
        return;
    }
    let mut i = 1;
    for (s, e) in START.iter().zip(END.iter()) {
        if i == n {
            writeln!(bufout, "{}n", s).unwrap();
            return;
        }
        writeln!(bufout, "{}{}", s, e).unwrap();
        i += 1;
    }
    let mut j = 1;
    while j <= 18 {
        let mut t = String::with_capacity(j + 2);
        for x in 0..j {
            let mut k = 0;
            for _ in 0..26 {
                for (s, e) in START.iter().zip(END.iter()) {
                    if i == n {
                        writeln!(bufout, "{}n", s).unwrap();
                        return;
                    }
                    t.clear();
                    t.push(*s);
                    for _ in 0..x {
                        if k == 26 { k = 0; }
                        t.push(ABC[k]);
                        k += 1;
                    }
                    for _ in 0..x {
                        if k == 26 { k = 0; }
                        k += 1;
                    }
                    if k == 26 { k = 0; }
                    let mut l = k;
                    for _ in 0..(j - x) {
                        if l == 26 { l = 0; }
                        t.push(ABC[l]);
                        l += 1;
                    }
                    k += 1;
                    t.push(*e);
                    writeln!(bufout, "{}", t).unwrap();
                    i += 1;
                }
            }
        }
        j += 1;
    }
    println!("{}", i)
}