using System;

public class Program

{

    private const double phi = (1 + 2.2360679774997896964091736687312) / 2;

    public static void Main()

    {

        Console.WriteLine(FindFibWithBinetFormula(26));

        Console.WriteLine(FindFibDynamically(26));

    }

    private static double FindFibWithBinetFormula(int n)

    {

        if (n == 1)

        {

            return 1;

        }

        return Math.Round(Math.Pow(phi, n) / Math.Sqrt(5));

    }

    private static int FindFibDynamically(int n)

    {

        var cache = new int[2];

        cache[0] = 1;

        cache[1] = 1;

        for (var i = 3; i <= n; i++)

        {

            cache[i % 2] = cache[0] + cache[1];

        }

        return cache[n % 2];

    }

}