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);
}
}