using System;

using System.Collections.Generic;

public class Program

{   

    public static void RemoveFifthAndSixth(List<int> list) 

    {

      list.RemoveAt(4);

      list.RemoveAt(4);

        foreach (int i in list)

            {   

                Console.WriteLine(i);

            }   

    }

    public static void RemoveMultipleOfThree(List<int> list) 

      {

         foreach (int i in list)

            {

                if(i%3!=0)

                Console.WriteLine(i);

            }   

    }

    static bool NotPrime(int x) {

        for(int a=2;a<x;a++){

            if( x%a==0)

                return true;

        }

                return false;

    }

    public static void Main() { 

          List<int> al = new List<int>(); 

          Random rand = new Random();

          int i=0;

          while(i<=9){

              int ran_num = rand.Next(2,51);    

              if(NotPrime(ran_num)&& !al.Contains(ran_num)){        

              al.Add(ran_num); 

              i++;

             }  

        }

                     foreach (int a in al)

             {

                Console.WriteLine(a);

             }

          Console.WriteLine("\n");    

          RemoveFifthAndSixth(al);

          Console.WriteLine("\n");  

          RemoveMultipleOfThree(al);    

      }

}

​

​