#include <iostream>
using namespace std;int main(){int a=1,b=1,c;cin>>c;for(int i=c-1;i;--i){swap(a,b);a+=b;}cout<<a<<endl;}
### Prompt

Your challenge is to write a Cpp solution to the following problem:

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

### Response

```cpp
#include <iostream>
using namespace std;int main(){int a=1,b=1,c;cin>>c;for(int i=c-1;i;--i){swap(a,b);a+=b;}cout<<a<<endl;}
```