#include <stdio.h>
#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 10000000


int main(){
	
	int N;
	cin>>N;
	
	if(N==1){
		cout<<0<<endl;
		return 0;
	}
	
	deque<long long> D(N);
	rep(i,N)D[i] = i+1;
	
	vector<long long> x,y;
	
	while(D.size()!=0){
		x.push_back(D.front());
		D.pop_front();
		if(D.size()==0)break;
		
		y.push_back(D.back());
		D.pop_back();
		if(D.size()==0)break;
		
		x.push_back(D.back());
		D.pop_back();
		if(D.size()==0)break;
		
		y.push_back(D.front());
		D.pop_front();
	}
	
	while(y.size()>0){
		x.push_back(y.back());
		y.pop_back();
	}
	
	x.push_back(1);
	
	
	long long ans = 0LL;
	
	rep(i,N){
		ans += x[i]*x[i+1];
		ans += x[i+1]-x[i];
	}
	
	cout<<ans<<endl;
	
    return 0;
}