#include <bits/stdc++.h>

using namespace std;

unsigned long long sumOfGroup(unsigned long long k)
{
    unsigned long long i,s=0,nr;
    i=(k-1)*k+1;
    nr=1;
    while(nr<=k)
    {
        s=s+i;
        i=i+2;
        nr++;
    }
    return s;
}
int main() {
    int k;
    cin >> k;
    long answer = sumOfGroup(k);
    cout << answer << endl;
    return 0;
}