#include<bits/stdc++.h>
using namespace std;
int main()
{
	int n,i,s=0,j=1;
	cin>>n;
	for(i=1;i<=n;i++){
		j*=i;
		if(i%2==1){
			s+=j;
		}else{
			s-=j;
		}
	}
	cout<<s;
	return 0;
}

/**************************************************************
	Problem: 1518
	User: zzz
	Language: C++
	Result: Accepted
	Time:10 ms
	Memory:2072 kb
****************************************************************/