Problems
Fibonacci Sequence
Fibonacci Sequence
The Fibonacci sequence is defined as follows:
\begin{itemize}
\item $a_0 = 0$,
\item $a_1 = 1$,
\item $a_k = a_{k-1} + a_{k-2}$
\end{itemize}
For a given value of $n$, find the $n$-th element of the Fibonacci sequence.
\InputFile
One positive integer $n~(1 \le n \le 40)$.
\OutputFile
Print the $n$-th element of the Fibonacci sequence.
Input example #1
2
Output example #1
1
Input example #2
5
Output example #2
5
Input example #3
8
Output example #3
21