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.*;

public class Main{

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long[] f = new long[21];
		f[0]=f[1]=1;
		for(int i=2;i<21;i++)f[i]=i*f[i-1];
		System.out.println(f[sc.nextInt()]);
	}
}