using System;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        var array = new [] {3, 2, 1, 1, 0, 4, 5, 2, 0};

        var hashSet = new HashSet<int>();

        foreach(var x in array)

        {

            if (!hashSet.Contains(x))

                hashSet.Add(x);

        }

        foreach(var x in hashSet)

            Console.WriteLine(x);

    }

}