using System;

using System.Collections.Generic;

​

public class Program

{

    static Dictionary<int,int> dict = new Dictionary<int,int>();

    public static void Main()

    {

        //Console.WriteLine("Hello World");

        /*Hashtable ht = new Hashtable();

        ht.Add("uno", 1);

        ht.Add("uno", "donas");

        Dictionary<int, int> dict = new Dictionary<int, int>();

        dict.Add(1,1);

        dict.Add(1,1);*/

        Add(1);

        Add(2);

        Add(3);

        Add(4);

        Add(4);

​

        Console.WriteLine(Find(9));

    }

    public static void Add(int input)

    {

        /*if(dict.ContainsKey(input))

            dict[input]++;

        else

            dict.Add(input, 1);*/

        int count = dict.ContainsKey(input) ? dict[input] : 0;

        dict[input] = count + 1;

    }

​

    public static bool Find(int val)

    {

        foreach(KeyValuePair<int,int> e in dict)

        {

            int num = e.Key;

            int y = val - num;

            if(y == num){

                if(e.Value >= 2) 

                    return true;

            }

            else if(dict.ContainsKey(y))

            {

                return true;

            }

        }

        return false;

    }

​

}