import java.util.Scanner;

/*
 * 使用for循环实现:
 * 根据用户输入的正整数n,求n!,
 * 即n!=n*(n-1)*(n-2)*…*1。(选做)
 */
public class Test14 {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int factorial = 1;
		for (int i = 1; i <= n; i++) {
			factorial *= i;
		}
		System.out.println(factorial);
	}

}