using System;
using System.Linq;

public class Test {
    static string Increment(string s) {
        if (s.All(c => c == 'z')) {
            return new string(Enumerable.Repeat('a', s.Length+1).ToArray());
        }
        var res = s.ToCharArray();
        var pos = res.Length - 1;
        do {
            if (res[pos] != 'z') {
                res[pos]++;
                break;
            }
            res[pos--] = 'a';
        } while (true);
        return new string(res);
    }

    public static void Main() {
	var s = "a";
        var i = 0;
        do {
            Console.Write(s+" ");
            if (++i == 26) {
                Console.WriteLine();
                i = 0;
            }
            s = Increment(s);
        } while (s != "faa");
    }
}