Dynamic Programming - Fibonacci Number

Time Limit : 1 sec, Memory Limit : 65536 KB
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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