using static System.Console;

using static System.Math;

public class Program {

    public static void Main() {

        for (int i = 0; i < 20; i++) WriteLine($"{Fib(i)}, {FibIte(i)}, {FibRec(i)}");

    }

    static int Fib(int n) {

        double sqrt5 = Sqrt(5);

        double p1 = (1 + sqrt5) / 2;

        double p2 = -1 * (p1 - 1);

        return (int)((Pow(p1, n) - Pow(p2, n)) / sqrt5);

    }

    static int FibIte(int n) {

        int a = 0;

        int b = 1;

        for (int i = 0; i < n; i++) {

            int temp = a;

            a = b;

            b = temp + b;

        }

        return a;

    }

    static int FibRec(int n) => n < 2 ? n : FibRec(n - 1) + FibRec(n - 2);

}