#include<cstdio> 
int F[50]={1,1};

int fib(int i){
	if(F[i]) return F[i];
	return F[i] = fib(i-1) + fib(i-2);
}
int main(){
	int n;
	scanf("%d",&n);
	printf("%d\n",fib(n));
}

### Prompt

In CPP, your task is to solve 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<cstdio> 
int F[50]={1,1};

int fib(int i){
	if(F[i]) return F[i];
	return F[i] = fib(i-1) + fib(i-2);
}
int main(){
	int n;
	scanf("%d",&n);
	printf("%d\n",fib(n));
}

```