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 Ruby (judge verdict: Accepted)

def fibonacci
	cache = {}
	fibo = lambda do |n|
		return 1 if n <= 1
		return cache[n] if cache.has_key?(n)

		cache[n] = fibo[n - 1] + fibo[n - 2]
	end
end

n = STDIN.gets.to_i
puts fibonacci.call(n)