#include<stdio.h>

void main(){
	int n,i,j,t=1,s=0,f;
	scanf("%d",&n);
	
	f=1;
	for(i=1;i<=n;i++){
		t=t*i;
		s=s+t*f;
		f=f*-1;
		}
	printf("%d",s);
}
/**************************************************************
	Problem: 1518
	User: admin
	Language: C
	Result: Accepted
	Time:15 ms
	Memory:1144 kb
****************************************************************/