#include <bits/stdc++.h>

using namespace std;

unsigned long long sumOfGroup(long k) {
    unsigned long long n,count=0,i;
    n=((k-1)*k);
    n=n+1;
    i=0;
    while(i<k)
    {
        count=count+n;
        n=n+2;
        i++;
    }
    return count;
}

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