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.math.*;
public class Main {

	/**
	 * @param args
	 */
	public static void main(String[] args)
			throws java.io.IOException{
		 BufferedReader d = new BufferedReader(new InputStreamReader(System.in));
		String n=d.readLine();
		System.out.println(fact(Integer.parseInt(n)));
		// TODO 自動生成されたメソッド・スタブ
		
	}
	
	public static long fact(int n){
		if(n==0) return 1;
		return n*fact(n-1);
		
	}

}