#include<stdio.h>
#include<string.h>
int main()
{
    long long k,sum,t,d,n;
    scanf("%lld",&k);
    d=(k*(k-1))/2;
    n=d+1;
    sum=1+(n-1)*2;
    sum=(k*((2*sum) + ((k-1)*2)))/2;
    printf("%lld\n",sum);
    return 0;
}