//template--------------------//
#include<bits/stdc++.h>
using namespace std;

#define gc getchar//_unlocked
#define pb push_back
#define mp make_pair
#define fi first
#define se second 
#define ll long long int
#define rep(i,s,e) for(i=s;i<e;i++)
#define all(c) c.begin(), c.end() 
#define revsort(v) std::sort(v.begin(), v.end(), std::greater<ll>());
#define tr(container, it)  for(typeof(container.begin()) it = container.begin(); it != container.end(); it++) 
#define present(c,x) ((c).find(x) != (c).end())
#define vpresent(container, element) (find(all(container),element) != container.end())
#define DBG cerr << "debug here" << endl;
#define DBGV(vari) cerr << #vari<< " = "<< (vari) <<endl;


typedef vector<int> vi;
typedef vector<ll> vl;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef vector<pii> vii;
typedef vector<pll> vll;

ll gcd(ll a,ll b){if(b==0)return a;return gcd(b,a%b);}
ll lcm(ll a,ll b){return((a*b)/gcd(a,b));}
//fast-IO
void scanint(int &x){register int c = gc();x = 0;int neg = 0;for(;((c<48 || c>57) && c != '-');c = gc());if(c=='-') {neg=1;c=gc();}
	for(;c>47 && c<58;c = gc()) {x = (x<<1) + (x<<3) + c - 48;}if(neg) x=-x;}


// template---------------------------//


int main(){
ios_base::sync_with_stdio(false);

    ll i,j,k;
    cin>>k;
    ll a = (k*(k-1))/2;
    a++;
    
    ll c=0,res=0;
    while(c<k){
        res += (2*a-1);
        //cout<<2*a-1<<" ";
        a++;c++;
    }

cout<<res<<endl;
	return 0;
}