public class Day9Recursion {

    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        int n = Integer.parseInt(br.readLine().trim());
        int result = Result.factorial(n);
        System.out.println(result);
        br.close();
    }

}


class Result {

    /*
     * Complete the 'factorial' function below.
     *
     * The function is expected to return an INTEGER.
     * The function accepts INTEGER n as parameter.
     */

    public static int factorial(int n) {
        // Base case
        if (n <= 1) {
            return n;
        } else {
            // Recursion
            // ie: 5
            // 5 * factorial(4)
            // 5 * 4 * factorial(3)
            // 5 * 4 * 3 * factorial(2)
            // 5 * 4 * 3 * 2 * factorial(1)
            // 5 * 4 * 3 * 2 * 1 => 120
            return n * factorial(n -1);
        }
    }

}