#include <bits/stdc++.h>

using namespace std;

long long sumOfGroup(long long k) {
    long long n,nr=0;
    unsigned long long sum=0;
    n=((k-1)*k)+1;
    while(nr!=k)
    {
        sum+=n;
        n=n+2;
        nr++;
    }
    return sum;
}

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