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.util.Scanner;
class Main {
	public static void main(String... args) {
		Scanner in = new Scanner(System.in);
		while(in.hasNext()) {
			int n = in.nextInt();
			long ans = 0;
			if(n > 0) {
				ans = 1;
				for(int i = 2; i <= n; i++) ans*=(long)i;
			}
			System.out.println(ans);
		}
	}
}