import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int i,sum1=0,sum2=0;
		sc.close();
		for(i=1;i<=n;i++) {
			if(i%2==0) {
				sum1+=jiecheng(i);
			}else {
				sum2+=jiecheng(i);
			}	
		}
		System.out.println(sum2-sum1);
	}
	public static int jiecheng(int n) {
		int i,s=1;
		for(i=1;i<=n;i++) {
			s*=i;
		}return s;
	}
}
/**************************************************************
	Problem: 1518
	User: admin
	Language: Java
	Result: Accepted
	Time:981 ms
	Memory:40192 kb
****************************************************************/