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 br=new BufferedReader(new InputStreamReader(System.in));
	long n=Integer.parseInt(br.readLine());
	System.out.println(factorial(n));
    }
    public static long factorial(long n){
	if(n<=1)
	    return 1;
	else
	    return n*factorial(n-1);
    }
}