#include<stdio.h>
int main()
{
	long long n, x, temp, num, sum;
	scanf("%lld", &n);
	temp=n-1;
	x = (temp*(temp+1))/2;
	num = (2*(x+1))-1;
	sum = n*(2*(num+(n-1)))/2;
	printf("%lld\n", sum);
}