Problem: It is November 18 now in Japan. By the way, 11 and 18 are adjacent Lucas numbers.

You are given an integer N. Find the N-th Lucas number.

Here, the i-th Lucas number L_i is defined as follows:

* L_0=2
* L_1=1
* L_i=L_{i-1}+L_{i-2} (i≥2)

Constraints

* 1≤N≤86
* It is guaranteed that the answer is less than 10^{18}.
* N is an integer.

Input

Input is given from Standard Input in the following format:


N


Output

Print the N-th Lucas number.

Examples

Input

5


Output

11


Input

86


Output

939587134549734843

Solution (in JAVA):

Solution:
import java.util.Scanner;
public class Main{

	static int []a;
	static int ans;
	static int count;
	public static void main(String[] args) {
		Scanner sc =  new Scanner(System.in);		//入s力
		int n = sc.nextInt();				//入力したのをint型に変換
		sc.close();
		long a0 = 2;
		long a1 = 1;
		long a2 = 0;
		if(n != 0){
			if(n != 1){
				for(int i = 0;i <= n-2;i++){
					a2 = a0 + a1;
					a0 = a1;
					a1 = a2;

				}
				System.out.println(a2);
			}else{
				System.out.println(a1);
			}
		}else{
			System.out.println(a0);
		}

	}



}