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 JavaScript (node.js v5.12) (judge verdict: Wrong Answer)

'use strict'

function main(input) {
    input = Number(input)

    let ans = 0
    let numbers = [2, 1]
    for (let i = 2; i <= input; i++) {
        let tmp = numbers[i - 2] + numbers[i - 1]
        // console.log(i, tmp)
        numbers.push(tmp)

    }

    console.log(numbers.pop())
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'))