int N = 3;
        string s = "";
        int[] arrayN = new int[] { 1, 2, 3 };
        for (int i = 0; i < N; i++)
        {
            s = s + arrayN[i];
            for (int j = 0; j < N; j++)
            {
                s = s + arrayN[j];
                for (int k = 0; k < N; k++)
                {
                    Console.Write(s + arrayN[k] + "n");
                }
                s = "";
                s = s + arrayN[i];
            }
            s = "";
        }