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 Kotlin (1.0.0) (judge verdict: Accepted)

import java.io.PrintWriter
val pw = PrintWriter(System.out)

fun main(args : Array<String>) {
    func()
    pw.flush()
}

fun func() {
    val n = nextInt()

    if (n == 1) {
        println(1)
        return
    }

    val ll = mutableListOf<Long>()

    ll.add(2L)
    ll.add(1L)

    for (i in 2..n) {
        ll.add(ll[i-1] + ll[i-2])
    }

    println(ll.last())
}

fun next() = readLine()!!
fun nextInt() = next().toInt()

fun println(value : Any) {
    pw.println(value)
}