#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) {
	long long int kk = (long long int)k;
	long long int m = kk*(kk-1)/2+1;
	long long int n = m+kk-1;
	m = 2*m-1;
	n = 2*n-1;
	return (long)((m+n)*kk/2);
}
int main() {
    int k;
    cin >> k;
    long answer = sumOfGroup(k);
    cout << answer << endl;
    return 0;
}