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.util.Scanner;
public class Main {
	public static void main(String[] a) {
		Scanner s=new Scanner(System.in);
		int n=s.nextInt(),i;
		long f=1;
		for(i=1;i<=n;i++)
			f=f*i;
		System.out.println(f);
	}
}