#include<bits/stdc++.h>
using namespace std;
#define ALL(x) x.begin(),x.end()
#define rep(i,n) for(int i=0;i<(n);i++)
#define debug(v) cout<<#v<<":";for(auto x:v){cout<<x<<' ';}cout<<endl;
#define INF 1000000000
#define mod 1000000007
using ll=long long;
const ll LINF=1001002003004005006ll;
int dx[]={1,0,-1,0};
int dy[]={0,1,0,-1};
ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
template<class T>bool chmax(T &a,const T &b){if(a<b){a=b;return true;}return false;}
template<class T>bool chmin(T &a,const T &b){if(b<a){a=b;return true;}return false;}

void exp(int n){
    vector<int> a(n);
    iota(ALL(a),1);
    int ans=INF;
    do{
        int cost=0;
        int pos=*a.begin();
        int wari=0;
        for(int i=1;i<n;i++){
            cost+=a[i]*pos+a[i]-pos;
            wari+=a[i]-pos;
            pos=a[i];
        }
        cost+=a[0]*a[n-1]+a[0]-a[n-1];
        wari+=a[0]-a[n-1];
        debug(a);
        cout<<cost<<" "<<wari<<endl;
        chmin(ans,cost);
    }while(next_permutation(ALL(a)));
    cout<<ans<<endl;
}

signed main(){
    cin.tie(0);
    ios::sync_with_stdio(0);

    int n;cin>>n;
    // exp(n);
    // 割引はどうでもいい

    if(n==1){
        cout<<0<<endl;
        return 0;
    }

    deque<int> deq,ans;
    rep(i,n) deq.push_back(i+1);
    bool f=true;
    while(!deq.empty()){
        if(f){
            ans.push_back(deq.back());
            deq.pop_back();
            if(!deq.empty()){
                ans.push_front(deq.front());
                deq.pop_front();
            }
            f=false;
        }else{
            ans.push_front(deq.back());
            deq.pop_back();
            if(!deq.empty()){
                ans.push_back(deq.front());
                deq.pop_front();
            }
            f=true;
        }
    }
    ll sum=0;
    rep(i,n){
        ll a=ans[i],b=ans[(i+1)%n];
        sum+=a*b;
    }
    cout<<sum<<endl;
    return 0;
}