int[] a = { 5, 3, 1, -1, -3, 3, 9, -4 };
            int teller = 0;
            Console.WriteLine("vul een getal in");
            int input = int.Parse(Console.ReadLine());
            int tellerTwee = 0;
            bool check = false;


            foreach(int getal in a)
            {

                if (getal == input)
                {
                    tellerTwee++;
                    check = true;

                }

            }

            int[] indexcheck = new int[tellerTwee];
            int indexchecklocation = 0;

            if (check == true)
            {
                foreach(int index in a)
                {
                    if (index == input)
                    {
                        indexcheck[indexchecklocation] = teller;
                        indexchecklocation++;
                    }
                    teller++;

                }

                Console.Write($"{input} is gevonden op index ");
                foreach(int output in indexcheck)
                {
                    Console.Write($"{output}, ");
                }

            }

            else
            {
                Console.WriteLine("niet gevonden");
            }