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)

input_str = STDIN.gets
n = input_str.to_i

$result = []
$result[0] = 1
$result[1] = 1
# for num in 2..n do
#   result[num] = result[num - 1] + result[num - 2]
# end
for i in 0..n do
  $result[i] = 0
end

$result[0] = 1
$result[1] = 1

def fib num
  if $result[num] != 0
    return $result[num]
  end
  a = fib (num - 1)
  b = fib (num - 2)
  $result[num] = a + b

  return $result[num]
end

fib n
puts $result[n]