#include<bits/stdc++.h>
#define mod ll(1e9+7)
#define sc(x) scanf("%d",&x)
#define pb push_back
#define mp make_pair
#define F first
#define S second
#define endl '\n'
#define pc putchar_unlocked
#define gc getchar_unlocked
#define gx getchar
#define be(v) v.begin(),v.end()
#define mem(s,v) memset(s,v,sizeof(s))
#define fr(i,a,n) for(int i=a;i<n;i++)
using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef pair<int,int> pi;
typedef pair<int,ll> pil;
typedef pair<ll,ll> pll;
typedef vector<pll> vpll;
typedef vector<pil> vpil;
typedef vector<pi> vpii;



int main() {
    ll k;
    cin >> k;
    ll done=(1ll*(k-1)*(k))/2;
    ll fi=2*(done+1)-1,ans=0;
    for(int i=0;i<k;i++)
    {
        ans+=(fi);
        fi+=2;
    }
    cout<<ans<<endl;
    return 0;
}