Lesson: array4

using System;

namespace CSLight3
{
    class Program
    {
        static void Main(string[] args)
        {
            int[] array = new int[0];
            int summ = 0;
            string input;

            while (true)
            {
                input = Console.ReadLine();

                switch (input)
                {
                    case "sum":
                        for (int i = 0; i < array.Length; i++)
                        {
                            summ += array[i];
                        }
                        Console.WriteLine("Сумма введенных чисел равна: " + summ);
                        summ = 0;
                        break;
                    case "exit":
                        Environment.Exit(0);
                        break;
                    default:
                        int[] tempArray = new int[array.Length + 1];
                        for (int i = 0; i < array.Length; i++)
                        {
                            tempArray[i] = array[i];
                        }
                        tempArray[tempArray.Length - 1] = Convert.ToInt32(input);
                        array = tempArray;
                        break;
                }
            }
        }
    }
}