#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(long k) {
    if(k == 1) return 1;
    long place = 0;
    for(long i = 1; i < k ; ++i) place += i;
    long start = 1 + 2*place;
    long sum = k*start + k*(k-1);
    return sum;
}

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