10. Array Manipulator

using System;
using System.Collections.Generic;
using System.Linq;

namespace _10.ArrayManipulator
{
    class ArrayManipulator
    {
        static void Main()
        {
            List<int> numbers = Console.ReadLine().Split(' ').Select(int.Parse).ToList();
            string[] commands = Console.ReadLine().Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries).ToArray();
            List<int> comand = new List<int>();
            int startPossition = 0;
            while (commands[0] != "print")
            {
                if (commands[0] == "addMany")
                {
                    foreach (var nums in commands)
                    {
                        if (nums == "addMany")
                        {
                            continue;
                        }
                        comand.Add(int.Parse(nums));
                        startPossition = comand[0];
                    }
                }
                switch (commands[0])
                {
                    case "add":
                        numbers = AddElement(int.Parse(commands[1]), int.Parse(commands[2]), numbers);
                        break;
                    case "contains":
                        Contains(int.Parse(commands[1]), numbers);
                        break;
                    case "remove":
                        numbers = Remove(int.Parse(commands[1]), numbers);
                        break;
                    case "addMany":
                        comand.RemoveAt(0);
                        numbers = AddMany(startPossition, comand, numbers);
                        comand = new List<int>();
                        break;
                    case "shift":
                        numbers = Shift(int.Parse(commands[1]), numbers);
                        break;
                    default:
                        numbers = SumPairs(numbers);
                        break;
                }
                commands = Console.ReadLine().Split(' ').ToArray();
            }

            Console.WriteLine("[{0}]", string.Join(", ", numbers));
        }
        private static List<int> Shift(int shiftCounts, List<int> numbers)
        {
            for (int i = 0; i < shiftCounts; i++)
            {
                int startPossition = numbers[0];
                numbers.RemoveAt(0);
                numbers.Add(startPossition);
            }
            return numbers;
        }

        private static List<int> AddMany(int possition, List<int> nums, List<int> numbers)
        {
            numbers.InsertRange(possition, nums);
            return numbers;
        }

        private static List<int> SumPairs(List<int> numbers)
        {
            List<int> sumNumbers = new List<int>();
            for (int i = 0; i < numbers.Count; i++)
            {
                if (i == numbers.Count - 1)
                {
                    break;
                }
                var sum = numbers[i] + numbers[i + 1];
                sumNumbers.Add(sum);
                i++;
            }
            if (numbers.Count % 2 == 0)
            {
                return sumNumbers;
            }

            sumNumbers.Add(numbers[numbers.Count - 1]);
            return sumNumbers;

        }
        private static List<int> Remove(int index, List<int> numbers)
        {
            numbers.RemoveAt(index);
            return numbers;
        }
        private static void Contains(int element, List<int> numbers)
        {
            Console.WriteLine(numbers.IndexOf(element));
        }
        private static List<int> AddElement(int index, int element, List<int> numbers)
        {
            numbers.Insert(index, element);
            return numbers;
        }
    }
}