using System;
using System.Linq;
using System.Collections.Generic;
 
public class Program
{
    public static IEnumerable<int> SpecialIndexes()
    {
        int i=4; 
 
        while (i<Int32.MaxValue)
        {
            yield return i++;
            yield return i++;
            i += 2;
        }
    }
 
    public static void Main(string[] args)
    {
        var csvString = "G9999999990001800002777107050,G9999999990002777107HMNLAQKPRLLHRAQRWJ010,1,3,29,P,6.74,11.23,07,P,5.25,14.29,08,P,6.89,16.92,07,P,5,4,";
 
        var fields = csvString.Split(',');
        var selected = SpecialIndexes()
            .TakeWhile(i => i<fields.Length)
            .Select(i => fields[i]);
 
        Console.WriteLine(string.Join(" ", selected.ToArray()));
    }
}
 

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