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
import java.io.*;
class Main
{
    public static void main(String args[])throws IOException
    {
	BufferedReader input=new BufferedReader(new InputStreamReader(System.in));
	int n=Integer.parseInt(input.readLine());
	long x=1;

	for(int i=n;i>0;i--)
	    {
		
		x*=i;
	    }
	
	System.out.println(x);
    }
}