#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(long k) {
     long  sum1 =k*(k-1)+1;
        long sum=0;
        for(long  i=0;i<k;i++){
                sum+=sum1;
                sum1=sum1+2;
        }
    return sum;
}

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