Ég Elska Forritun 1

using System;
using System.Collections.Generic;
using System.Numerics; // Þarf að refrencea

public class Program
{
    public void main()
        {
        Console.WriteLine(Poss(0, 0));
        Console.ReadLine();
        }

        private Dictionary<string, BigInteger> Mem = new Dictionary<string, BigInteger>();

        public BigInteger Poss(int x, int y)
        {
            if (x == 100 && y == 100) return BigInteger.One;

            string k = x > y ? x.ToString() + "," + y.ToString() : y.ToString() + "," + x.ToString();
            if (Mem.ContainsKey(k)) return Mem[k];

            BigInteger n = BigInteger.Zero;
            if (x <= 99 && y <= 99) n += Poss(x + 1, y + 1);
            if (x <= 99) n += Poss(x + 1, y);
            if (y <= 99) n += Poss(x, y + 1);

            Mem.Add(k, n);
            return n;
        }
}