Problem:
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Fibonacci Number

Write a program which prints $n$-th fibonacci number for a given integer $n$. The $n$-th fibonacci number is defined by the following recursive formula:

\begin{equation*}
fib(n)= \left \{
\begin{array}{ll}
1　 & (n = 0) \\
1　 & (n = 1) \\
fib(n - 1) + fib(n - 2) & \\
\end{array}
\right.
\end{equation*}

Input

An integer $n$ is given.

output

Print the $n$-th fibonacci number in a line.

Constraints

$0 \leq n \leq 44$

Sample Input 1

3

Sample Output 1

3

Solution in Kotlin (judge verdict: Accepted)

fun main(args: Array<String>) {
    val n = readLine()?.toInt() ?: return
    val fibonacci = Fibonacci()
    println(fibonacci.getFibonacci(n))
}

class Fibonacci {
    private val fibonacciMemo = mutableMapOf(0 to 1, 1 to 1)

    fun getFibonacci(n: Int): Int {
        return if (fibonacciMemo[n] != null) {
            fibonacciMemo[n]!!
        } else {
            fibonacciMemo[n] = getFibonacci(n - 2) + getFibonacci(n - 1)
            fibonacciMemo[n]!!
        }
    }
}