#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) {
    // Return the sum of the elements of the k'th group.
    long long int n,a,l,sum,kk;
kk=k;
     n= (kk*(kk-1))/2;
    a=2*n+1;
    l=a+(2*(k-1));
    sum=((kk)*(a+l))/2;
   // sum=sum%(1000000007);
  //  printf("%d %lld %lld %lld %lld",k,a,l,sum,n);
    return sum;

}

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