백준 9단계 no.1

import java.util.*;

public class Main {
    static int factorial(int n) {
        if (n <= 1) {
            return 1;
        } else {
            n = n * factorial(n - 1);
        }
        return n;
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt();

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