#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) {
	long pre = 1;
	long ans = 0;
	int i;
	for (i = 0; i < k ; i++) {
		//cout << i;
		pre += 2;
	}
	//ans = pre;
	for (int j = 0; j < k; j++) {
		ans += pre;
		pre += 2;
	}
	//cout << pre << endl;
	return ans;
}

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