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$& (n = 0) \\ 1 & (n = 1) \\ fib(n - 1) + fib(n - 2) & \$\end{array} \right. \end{equation*}$

Constraints

• $0 \leq n \leq 44$

Input

An integer $n$ is given.

Example

Input

3

Output

3

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