# 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

## Sample Input 1

3

## Sample Output 1

3