#include <bits/stdc++.h>

using namespace std;

long long sumOfGroup(long long k) {
    // Return the sum of the elements of the k'th group.
    long long num=(k-1)*k/2;
    long long kth=2*num-1+2;
    long long ans=(2*kth + (k- 1)*2)*k/2;
    return ans;
}

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