using System;

using System.Collections.Generic;

using System.Numerics;

​

namespace Training_Project

{

    internal class Program

    {

        static Dictionary<int, BigInteger> _fibonacciOfNumber = new();

​

        static void Main(string[] args)

        {

            Console.WriteLine(Fib(512));

        }

​

        static BigInteger Fib(int n) 

        {

            if (n <= 2)

            {

                return 1;

            }

​

            if (!_fibonacciOfNumber.ContainsKey(n))

            {

                _fibonacciOfNumber[n] = Fib(n - 1) + Fib(n - 2);

            }

​

            return _fibonacciOfNumber[n];

        }

    }

}

​