#include <bits/stdc++.h>

using namespace std;

long long sumOfGroup(int K) {
    // Return the sum of the elements of the k'th group.
    long long  k=K;
    k--;
    long long m=k*(k+1);
    m=m/2;
    m=m+1;
   long  long t=1LL+(m-1)*2LL;
   long  long sum=K*((2LL*t)+2LL*(K-1LL));
    sum=sum/2LL;
    return sum;
}

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