#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i = 0;i<((int)(n));i++)
#define reg(i,a,b) for(int i = ((int)(a));i<=((int)(b));i++)
#define irep(i,n) for(int i = ((int)(n)-1);i>=0;i--)
#define ireg(i,a,b) for(int i = ((int)(b));i>=((int)(a));i--)
typedef long long ll;

/*
*/

ll n,ans=0;

void init(){
	cin>>n;
}

int main(void){
	init();
	if(n==1){
		ans=0;
	}else if(n%2==0){
		ll a=n/2,b=n/2+1;
		ans+=a*b;
		rep(i,n/2-1){
			ans+=a*(b+1) + (a-1)*b;
			a--;
			b++;
		}
		ans+=n;
	}else{
		ll a=n/2+1,b=n/2+1;
		rep(i,n/2){
			ans+=a*(b+1) + (a-1)*b;
			a--;
			b++;
		}
		ans+=n;
	}
	cout<<ans<<endl;
	return 0;
}