#include <bits/stdc++.h>
using namespace std;

long long sumOfGroup(int k) {
	long long cur = 1;
	for (int i = 1; i < k; i++)
		cur += 2 * i;

	long long sum = (cur + cur + 2 * (k - 1)) * k / 2;
    return sum;
}

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