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.*;
public class Main {
    public static void main(String[] args) throws IOException {
    	System.out.println(fact(Integer.parseInt((new BufferedReader(new InputStreamReader(System.in))).readLine())));}
    private static long fact(int n){return (n==0)?1:n*fact(n-1);}
}