/******************************************
*    AUTHOR:         CHIRAG AGARWAL       *
*    INSTITUITION:   BITS PILANI, PILANI  *
******************************************/
#include <bits/stdc++.h>
using namespace std;
 
typedef long long LL; 
typedef long double LD;

int main() 
{
    int k;
    scanf("%d",&k);
    LL cur=((k*1ll*(k-1))/2);
    cur=2*cur-1;
    LL ans=0;
    for(int i=1;i<=k;i++)
    {
        ans+=(cur+2*i);
    }
    printf("%lld\n",ans);

    return 0;
}