4数字能组成多少无重复的三位数

 for(int i= 1;i<5;i++)
            {
                for (int j = 1; j < 5; j++)
                {
                    if (j == i)
                        continue;
                    else
                    {
                        for (int k = 1; k < 5; k++)
                        {
                            if (k == j || k == i)
                                continue;
                            else
                                Console.WriteLine(i.ToString()+j.ToString()+k.ToString());
                        }
                    }
                }
            }