using System;
using System.Collections.Generic;
public class Program
{
public static void Main()
{
string[] words = { "alga", "ajka", "aoia", "apal", "aeal", "aatl", "aaul", "gaal", "laaj", "lata", "laoa" };
char letter = 'a';
int pos = 3;
List<string> wordFamilies = new List<string>();
foreach (var word in words)
{
if (pos < word.Length && word[pos] == letter)
wordFamilies.Add(word);
}
Console.WriteLine(string.Join(",", wordFamilies));
}
}