#include<iostream>
using namespace std;
int main()
{
 	unsigned long long int k;
	scanf("%lu",&k);
	unsigned long long int start=k*(k-1);
	//printf("start:%d\n",start);
//	cout<<"Start:"<<start<<endl;
	int i;
	 start+=1;
	unsigned long long int sum=0;
	//int sum=start;
	for(i=0;i<k;i++)
	{	
		sum=sum+start;
	//	cout<<"odd:"<<start<<endl;
		start=start+2;
		//cout<<"sum:"<<sum<<endl;
		//sum+=(start+2);
	}
	cout<<sum;
	return 0;
}