#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(long k) {
    // Return the sum of the elements of the k'th group.
    if(k==0)
        return 0;
    long i=(k*(k-1))/2;
    long t=1+i*2;
    long las=t+(k-1)*2;
    long result=(k*(t+las))/2;
                 return result;
}

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