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 {



    public static void main(String[] args) {
    	Scanner input = new Scanner(System.in);
    	int n = input.nextInt();
    	long[] num = new long[n + 1];
    	num[0] = 2l;
    	num[1] = 1l;
    	for (int i = 2; i <= n; i++) {
    		num[i] = num[i-1] + num[i - 2];
    	}
     	System.out.println(num[n]);
    }
}