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 in = new Scanner(System.in);

      int N = in.nextInt();
      long ans[] = new long[87];

      ans[0] = 2;
      ans[1] = 1;

      for(int cnt = 2; cnt <= N; cnt++) {
          ans[cnt] = ans[cnt-1] + ans[cnt-2];
      }

      System.out.println(ans[N]);

    }
}