#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) {
    long long int x=k-1;
    long long int startindex=x*(x+1)/2;
    startindex+=1;
    long long int endindex=startindex+k-1;
    long long int sum=2*startindex-1+2*endindex-1;
    sum=sum*k;
    sum=sum/2;
    return sum;
    // Return the sum of the elements of the k'th group.
}

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