#include <bits/stdc++.h>
#include <atcoder/all>

typedef unsigned long long ULLONG;
typedef long long LLONG;
static const LLONG MOD_NUM = 1000000007LL;//998244353LL;
static const LLONG INF_NUM = MOD_NUM * 20LL;
template<class _T> static void get(_T& a) {
	std::cin >> a;
}
template<class _T> static void get(_T& a, _T& b) {
	std::cin >> a >> b;
}
template<class _T> static void get(_T& a, _T& b, _T& c) {
	std::cin >> a >> b >> c;
}
template <class _T> static _T tp_abs(_T a) {
	if (a < (_T)0) {
		a *= (_T)-1;
	}
	return a;
}

static void task();

int main()
{
	task();
	fflush(stdout);
	return 0;
}

static void task()
{
	ULLONG K;
	get(K);

	if (K == 1) {
		printf("6\n");
		return;
	}

	ULLONG last = 4 + 8 * (K - 1);
	ULLONG sum = (K - 1ULL) * (12ULL + last) / 2ULL;
	printf("%llu\n", sum + 6ULL);
}