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.*;

class Main{
public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    long[] L = new long[n+1];
    L[0] = 2;
    L[1] = 1;
    if(n == 1) {
    	System.out.println(1);
    } else {
        for(int i = 2; i <= n; i++) {
        	L[i] = L[i-1] + L[i-2];
        	if(i == n) {
        		System.out.println(L[i]);
        	}
        }
    }
}
}