#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) {
    // Return the sum of the elements of the k'th group.kk) 
    k = k-1;
    long first = 1 + 2* (long(k) * (k+1)/2);
    long result=first;
    for(auto i=1; i <= k; i++)
    {
        first += 2;
        result += first;
    }
    return result;
}

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