using System;

using System.Collections.Generic;

using System.Linq;

​

​

public class Program

{

    public static void Main()

    {

        Dictionary<string, string> offSpringBreedPurity = new Dictionary<string, string>();

        Dictionary<string, string> SireBreedPurity = new Dictionary<string, string>();

        Dictionary<string, string> DamBreedPurity = new Dictionary<string, string>();

        SireBreedPurity.Add("SN","50");

        SireBreedPurity.Add("LM","50");

        //DamBreedPurity.Add("SN","100");

        //DamBreedPurity.Add("TB","50");

        offSpringBreedPurity = SireBreedPurity.Concat(DamBreedPurity)

                .GroupBy(x => x.Key)

                .ToDictionary(x => x.Key

                              , x => 

                              (x.Count() > 1 ? 

                               x.Average(y => Convert.ToInt64(y.Value))

                               : Convert.ToInt64(x.Last().Value)/2

                              ).ToString());

​

        Console.WriteLine(offSpringBreedPurity["SN"]);

        Console.WriteLine(offSpringBreedPurity["LM"]);

        //Console.WriteLine(offSpringBreedPurity["TB"]);

    }

}