#include <bits/stdc++.h>
#include<iostream>
#include<cmath>
using namespace std;

long sumOfGroup(int k) {
    int i;
    long out1=pow(k,2)-(k-1);
    //cout<<out1;
    long out2=out1;
    for(i=1;i<k;i++)
    {
        out2=out2+2;
        out1=out1+out2;
    }
    return out1;
    // Return the sum of the elements of the k'th group.
}

int main() {
    int k;
    cin >> k;
    long answer = sumOfGroup(k);
    cout << answer << endl;
    return 0;
}