int[] nums = new int[5];
            int a;
            int arraySeq;
            int target;
            bool reset = true;

            do
            {
                for (arraySeq = 0; arraySeq < nums.Length; arraySeq++)
                {
                    for (a = 1; a <= arraySeq; a++) { }

                    Console.Write("insert the number #" + a + " = ");
                    nums[arraySeq] = int.Parse(Console.ReadLine());
                    for (int i = 0; i < arraySeq; i++)
                    {
                        if (nums[arraySeq] == nums[i])
                        {
                            reset = true;
                            Console.WriteLine("You can't insert the same number");
                            Console.ReadKey();
                            Console.Clear();

                        }
                        else
                        {
                            reset = false;
                        }
                    }
                }
            }while(reset == true);