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.*;

public class Main {
	static long A[] = new long[87];
	
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		System.out.println(l(N));
	}
	
	public static long l(int n) {
		if (A[n] != 0) {
			return A[n];
		}
		
		long ans;
		if (n == 0) {
			ans = 2;
		} else if (n == 1) {
			ans = 1;
		} else {
			ans = l(n - 2) + l(n - 1);
		}
		A[n] = ans;
		
		return ans;
	}
}