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;

final class Main {

    private Main() {
    }

    public static void main(final String[] argv) throws IOException {
        final BufferedReader inputReader =
                new BufferedReader(new InputStreamReader(System.in));
        System.out.println(factorial(Integer.parseInt(inputReader.readLine())));
    }
    public static long factorial(long n) {
        if (n <= 1) return 1;
        return n * factorial(n - 1);
    }
}