Array Manipulator - 66%

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;


class Array_Manipulator
{
    static void Main()
    {
        List<int> nums = Console.ReadLine().Split().Select(int.Parse).ToList();

        while (true)
        {
            string[] commands = Console.ReadLine().Split().ToArray();
            string command = commands[0];
            if (command == "print") break;
            if (command == "add")
            {
                add(nums, commands);
            }
            else if (command == "addMany")
            {
                addMany(nums, commands);
            }
            else if (command == "contains")
            {
                contains(nums, commands);
            }
            else if (command == "remove")
            {
                remove(nums, commands);
            }
            else if (command == "shift")
            {
                shift(nums, commands);
            }
            else if (command == "sumPairs")
            {
                nums = sumPairs(nums);
            }
        }
        Console.WriteLine("[" + string.Join(", ", nums) + "]");
    }

    private static List<int> sumPairs(List<int> nums)
    {
        List<int> summed = new List<int>();
        while (nums.Count >= 2)
        {
            summed.Add(nums[0] + nums[1]);
            nums.RemoveAt(0);
            nums.RemoveAt(0);
        }
        nums = summed;
        return nums;
    }

    private static void shift(List<int> nums, string[] commands)
    {
        int numberOfPositions = int.Parse(commands[1]);
        while (numberOfPositions > 0)
        {
            int first = nums[0];
            nums.RemoveAt(0);
            nums.Add(first);
            numberOfPositions--;
        }
    }

    private static void remove(List<int> nums, string[] commands)
    {
        int index = int.Parse(commands[1]);
        nums.RemoveAt(index);
    }

    private static void contains(List<int> nums, string[] commands)
    {
        int element = int.Parse(commands[1]);
        if (nums.Contains(element))
        {
            Console.WriteLine(nums.IndexOf(element));
        }
        else Console.WriteLine("-1");
    }

    private static void addMany(List<int> nums, string[] commands)
    {
        int index = int.Parse(commands[1]);
        for (int i = commands.Length - 1; i >= 2; i--)
        {
            int element = int.Parse(commands[i]);
            nums.Insert(index, element);
        }
    }

    private static void add(List<int> nums, string[] commands)
    {
        int index = int.Parse(commands[1]);
        int element = int.Parse(commands[2]);
        nums.Insert(index, element);
    }
}