#include <iostream>

using namespace std;

int main(){
  long long int a = 1, b = 1;
  int n; cin >> n;

  for(int i=0;i<n;++i){
    long long int c = a + b;
    a = b;
    b = c;
  }
  cout << a << endl;

  return 0;
}
### 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(){
  long long int a = 1, b = 1;
  int n; cin >> n;

  for(int i=0;i<n;++i){
    long long int c = a + b;
    a = b;
    b = c;
  }
  cout << a << endl;

  return 0;
}
```