using System;

using System.Collections.Generic;   

public class Program

{

    public static void Main()

    {

        int i = 0;

        List<char> codes = new() { '1', 'a', 'b', 'c', '2', };

        List<char> numbers = new() { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' };

        foreach (char code in codes)

        {

                foreach (char element in numbers)

                { 

                    while ( i < 2 ) 

                    {

                        if ( element == code )

                            {

                                Console.WriteLine($"{code}");

                                i++;

                            }

                    }

                }

        }

    }

}

/*

1abc2

pqr3stu8vwx

a1b2c3d4e5f

treb7uchet

*/

​