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{

    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        long[] num = new long[100];

        for(int i =0;i<100;i++){
            if(i==0){
                num[i]=2;
            }else if(i==1){
                num[i]=1;
            }else{
            num[i] = num[i-1]+num[i-2];
        }
    }

        System.out.println(num[n]);
        

    }
}