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
class Main{public static void main(String[]a){long r=1,i=0,t=new java.util.Scanner(System.in).nextInt();for(;i++<t;r*=i);System.out.println(r);}}