using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

         string str = "ABCD";

         List<string> char_list = new List<string>();

         for (int i = 0; i < str.Length; i++)

            char_list.Add(str[i].ToString());

         foreach (var permutation in new Combinatorics.Collections.Permutations<string>(char_list))

            Console.WriteLine(String.Join("", permutation));

    }

}