using System;

using System.Collections.Generic;

public class Program

{

    static Dictionary<int, List<int>> d;

    static void Add(int key, int val)

    {

        List<int> lst;

        if (d.TryGetValue(key, out lst) == false)

        {

            lst = new List<int>();

            d.Add(key, lst);

        }

        lst.Add(val);

    }

    public static void Main()

    {

        d = new Dictionary<int, List<int>>();

        Add(0, 3);

        Add(0, 4);

        Console.WriteLine("List: {0}, {1}", d[0][0], d[0][1]);

    }

}