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 scan = new Scanner(System.in);
		int n = scan.nextInt();
		scan.close();

		long l[]=new long[n+1];
		l[0]=2;
		l[1]=1;
		for(int i=2;i<=n;i++) {
			l[i]=l[i-1]+l[i-2];
		}
		System.out.println(l[n]);
		//System.out.println(func(n));
	}

	/*
	static long func(int n) {
		if(n==0)return 2;
		if(n==1)return 1;
		return func(n-1)+func(n-2);
	}*/
}