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.io.FileInputStream;
import java.io.InputStream;
import java.util.Scanner;

public class Main {
	static Scanner sc;

	public static void main(String[] args) throws Exception {
		//InputStream in = new FileInputStream("src/input.txt");
		InputStream in = System.in;

		sc = new Scanner(in);

		int N = sc.nextInt();

		long[] L = new long[N+1];

		L[0] = 2;
		L[1] = 1;
		for(int i = 2; i <= N; i++){
			L[i] = L[i-2] + L[i-1];
		}
		System.out.println(L[N]);
	}
}