using System;

using System.Linq;

public class Program

{

    public static void Main()

    {

        int[] elements = { 5, 4, 2, 2, 1, 5, 4, 3, 3, 4, 4, 3, 5, 5, 5 };

        int n = 3;

        int rarest = elements.GroupBy(x => x).OrderBy(x => x.Count()).Skip(n - 1).FirstOrDefault().Key;

        Console.WriteLine(rarest);

    }

}