#include <bits/stdc++.h>

using namespace std;

long k;
long sumOfGroup(long k)
{
    k-=1;
    long sta=k*(k+1)/2,s=0,d=0;
    for (int i=sta*2;i<=10000000;i++)
    if (i%2>0)
    {
        s+=i;
        d++;
        if (d==k+1) break;
    }
    return(s);
}

int main()
{
    ios::sync_with_stdio(false);cin.tie(0);
    cin >> k;
    long answer = sumOfGroup(k);
    cout << answer << endl;
    return 0;
}