#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(long k) {
   long sum=0;
    for(long i=(k*k-(k-1));i<=(k*k+(k-1));i+=2)
    {
        sum+=i;
    }
    return sum;// Return the sum of the elements of the k'th group.
}

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