#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) {
    // Return the sum of the elements of the k'th group.
    long long int sum=0,s;
    s=pow(k,2)-(k-1);
      //  cout<<" "<<s;
    int i;
    for(i=0;i<k;i++)
    {    sum+=s;
    s+=2;
    }
    return sum;
}

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