package 练习;

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int q = 1,h=1,i=3;
        if(n==1||n==2)
        {
            System.out.println(String.format("%.2f",1.00));
        }
        else if(n==0)
        {
            System.out.println(String.format("%.2f",0.00));
        }
        else
        {
            while(i<=n)
            {
                int t = q;
                q=h;
                h=t+h;
                i++;
            }
            System.out.println(String.format("%.2f",(double)h));
        }
    }
}