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

#define forn(i,n) for(tint i=0;i<(tint)(n); i++)
#define forsn(i,s,n) for(tint i=(s);i<(tint)(n); i++)
#define debug(x) cout << #x << " = "  << x << endl
#define pb push_back
#define mp make_pair
typedef long long tint;
int toNumber (string s)
{
	int Number;
	if ( ! (istringstream(s) >> Number) ) Number = 0; // el string vacio lo manda al cero
	return Number;
}
string toString (int number)
{
    ostringstream ostr;
    ostr << number;
    return  ostr.str();
}

tint ele(tint a, tint b){
	if(b==0)return 1;
	if(b%2==0){
		return ele((a*a), b/2);
	}else{
		return a*ele((a*a), b/2);
	}
}

tint mcd(tint a, tint b){
	if(a==0)return b;
	return mcd(b%a, a);
}

double d_abs(long a, long b){
	if(a>b){
		return a-b;
	}
	return b-a;
}

int main(){
	tint k;
	cin>>k;
	tint antes = k*(k-1)/2;
	tint su=0;
	forsn(i, antes+1, antes+1+k){
		su+=(i*2-1);
	}
	cout<<su<<endl;
}