using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        int[] nums = new[] { 1, 1, 1, 2, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7 };

    var intermediate = nums

                .GroupBy(i => i)

                .Select(g => (g.Key,g.Count()));

    int amount = intermediate.Max(x => x.Item2);

    IEnumerable<int> mostFrequent = intermediate

                .Where(x => x.Item2 == amount)

                .Select(x => x.Item1);

        Console.WriteLine(string.Join(" ", mostFrequent));

    }

}