#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) {
    // Return the sum of the elements of the k'th group.
    long lastNumber = 0, totalElements = 0, sumOfK = 0;
    for (int i = k; i >= 1; i--) {
        totalElements += i;
    }
    lastNumber = totalElements * 2 - 1;
    
    for (int i = 0; i < k; i++) {
        sumOfK += lastNumber;
        lastNumber -= 2;
    }
    return sumOfK;
}

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