#include <iostream>

#define DEBUG false


using namespace std;

int main() {


	long long k;
	cin >> k;
	
	long long startTerm = ((k-1) * ((k-1) + 1 ) / 2) + 1;
	
	if(DEBUG) cout << "startTerm: " << startTerm << endl;
	
	long long startValue = 2 * (startTerm) - 1;
	
	if(DEBUG) cout << "startValue: " << startValue << endl;
	
	long long result =  k * (startValue + k - 1);
	
	cout << result;
	
	return 0;
	
}