#include <iostream>
using namespace std;
typedef unsigned long long ULL;
int main(){
	ULL a=1,b=1,c,n;
	cin>>n;
	for (ULL i=1;i<=n;++i){
		c=a+b;
		a=b;
		b=c;
	}
	cout<<a<<endl;
	return 0;
}
### Prompt

Your task is to create 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;
typedef unsigned long long ULL;
int main(){
	ULL a=1,b=1,c,n;
	cin>>n;
	for (ULL i=1;i<=n;++i){
		c=a+b;
		a=b;
		b=c;
	}
	cout<<a<<endl;
	return 0;
}
```