#include <stdio.h>
#include <math.h>
#include <stdlib.h>


int main()
{
	int k;
	scanf("%d", &k);

	long num = 0;
	long long sum = 0;

	for (long i = 1; i < k; i++)
	{
		for (long j = 1; j <= i; j++)
		{	
			num += 2;
		}
	}
	num++;

	for (long i = 0; i < k; i++)
	{
		sum += num;
		num += 2;
	}
	printf("%lld\n", sum);
	
}