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 sc = new Scanner(System.in);

		//リュカ数の配列を作成
		long L0 = 2;
		long L1 = 1;
		long L2;

		long[] numList = new long[86];

		numList[0] = L1;

		for (int i=1; i < 86; i++){
			L2 = L0 + L1;

			numList[i] = L2;

			L0 = L1;
			L1 = L2;
		}

		// 整数の入力
		int n = sc.nextInt();

		System.out.println(numList[n-1]);

		sc.close();
	}

}