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.*;
import java.util.*;
class Main{
    public static void main(String args[]){
	Scanner scan = new Scanner(System.in);
	long n = scan.nextInt();
	long ans = sub(n);
	System.out.println(ans);
    }
    
    public static long sub(long n){
	if(n > 0){
	    return n * sub(n-1);
	}
	else{
	    return 1;
	}
    }
}