#include <iostream>
using namespace std;
long long f(int n)
{
	return(n?n*f(n-1):1);
}
int main()
{
	int n;
	cin >> n;
	cout << f(n) << endl;
	
	return 0;
}
### Prompt

Construct a CPP code solution to the problem outlined:

Write a program which reads an integer n and prints the factorial of n. You can assume that n ≤ 20.



Input

An integer n (1 ≤ n ≤ 20) in a line.

Output

Print the factorial of n in a line.

Example

Input

5


Output

120

### Response

```cpp
#include <iostream>
using namespace std;
long long f(int n)
{
	return(n?n*f(n-1):1);
}
int main()
{
	int n;
	cin >> n;
	cout << f(n) << endl;
	
	return 0;
}
```