using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

            FindOneOne obj = new FindOneOne();

            obj.Run();

    }

}

​

​

    public class FindOneOne

    {

        public void Run() {

            int result = Find(5);

            Console.WriteLine(result);

            Console.ReadLine();

        }

​

        public int Find(int n) {

            int a = 1;

            int b = 1;

​

            if (n == 1)

                return a + b;

​

            for (int i = 1; i < n; i++) {

                int prevA = a;

                a = b;

                b= prevA + b;

            }

​

            return a + b;

        }

    }