Array Search

using System;
using System.Linq;

namespace Array_Search
{
    class Program
    {
        static void Main(string[] args)
        {
            int[] numbers = Console.ReadLine().Split(',').Select(int.Parse).ToArray();
            string result = string.Empty;

            for (int i = 1; i <= numbers.Length; i++)
            {
                bool isThere = false;
                for (int j = 0; j < numbers.Length; j++)
                {
                    if(i==numbers[j])
                    {
                        isThere = true;
                        break; ;
                    }
                }
               if (isThere==false)
                {
                    result += i+",";
                }


            }
            result=result.Trim(result[result.Length - 1]);
            Console.WriteLine(result);
        }
    }
}