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 fib n
  dp = Array.new(n + 1)
  0.upto(n) do |i|
    dp[i] = if i == 0 || i == 1
              1
            else
              dp[i - 1] + dp[i - 2]
            end
  end
  dp[n]
end

n = gets.chomp.to_i
puts fib(n)