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.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;


public class Main{
	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String str = br.readLine();
		int n = Integer.parseInt(str);

		System.out.println(fac(n));
	}

	static long fac(int n){
		if(n==0){
			return 1;
		}else{
			return n*fac(n-1);
		}
	}

}