using System;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var scores = new Dictionary<string, int>{

            {"a", 2},

            {"b", 2},

            {"c", 1},

            {"d", 0},

        };

        var max = scores.Values.Max();

        Console.WriteLine(string.Join(" ", scores.Where(s => s.Value == max).Select(s => s.Key)));

    }

}