#include <bits/stdc++.h>

using namespace std;

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

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