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);
        long n = sc.nextInt();

        long ans = fib(n);


        System.out.println(ans);
    }

    public static long fib(long n) {
       long dp[] = new long[(int)(n+1)];

       dp[0] = 2;
       dp[1] = 1;

       for (long i = 2; i < n + 1; i++) {
           dp[(int)i] = dp[(int)(i - Long.valueOf(1))] + dp[(int)(i - 2)];
       }

       return dp[(int)n];

    }
}