Problem:
Score : 200 points

Problem Statement

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.

Sample Input 1

5

Sample Output 1

11

L_0=2

L_1=1

L_2=L_0+L_1=3

L_3=L_1+L_2=4

L_4=L_2+L_3=7

L_5=L_3+L_4=11

Thus, the 5-th Lucas number is 11.

Sample Input 2

86

Sample Output 2

939587134549734843

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)

import  java.util.*;
 
public class Main{
	public static void main(String[] args){
    	Scanner scan = new Scanner(System.in);
      	int a = scan.nextInt();
      	int prepre = 2;//n-2
      	int pre = 1;//n-1
      	int now = 3;
      	if(a == 0){
        	System.out.print(prepre);
        }
      	else if(a == 1){
        	System.out.print(pre);
        }
      	else{
      		for(int i = 2; i < a; i++){
        		prepre = pre;
          		pre = now;
              	now = prepre + pre;
       	 	}
          	System.out.print(now);
        }
    	
    }
 
}