#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<n;i++)
using namespace std;
using ll = long long ;
using P = pair<int,int> ;
const int INF = 1e9;
const int MOD = 1000000007;

int main(){
    int n;
    cin >> n;
    if(n==1){
        cout << 0 << endl;
        return 0;
    }
    deque<ll> dq;
    dq.push_back(n);
    int l = 1,r = n-1;
    while(l <= r){
        dq.push_back(l);
        ++l;
        if(l > r) break;
        dq.push_front(l);
        ++l;
        if(l > r) break;
        dq.push_back(r);
        --r;
        if(l > r) break;
        dq.push_front(r);
        --r;
        if(l > r) break;
    }
    ll ans = 0;
    rep(i,n){
        if(i==n-1) ans += dq[i] * dq[0];
        else ans += dq[i]*dq[i+1];
    }
    cout << ans << endl;
    return 0;
}