Задание Search1, Поиск и сортировка

using System;
using System.Collections.Generic;

namespace classwork2
{
    class Program
    {
        static void Main()
        {
            var initialArray = new int[9] { 1, 2, 9, 8, 9, 9, 4, 2, 2 };
            var arrayIndexes = ArrayIndexesNumbers(initialArray);

            var numberInput = int.Parse(Console.ReadLine());
            if (arrayIndexes.ContainsKey(numberInput))
            {
                var index = arrayIndexes[numberInput];
                Console.WriteLine(index);
            }
            else
                Console.WriteLine(-1);
        }

        public static Dictionary<int, int> ArrayIndexesNumbers(int[] initialArray)
        {
            var arrayIndices = new Dictionary<int, int>();

            for (var index = 0; index < initialArray.Length; index++)
            {
                var number = initialArray[index];
                if (!arrayIndices.ContainsKey(number))
                    arrayIndices[number] = index;
            }
            return arrayIndices;
        }
    }
}