#include <bits/stdc++.h>

using namespace std;
long sum_func(long int n){
    return (n*n);
}

long sumOfGroup(long int k) {
    if(k==1)
        return 1;
    else if(k==2)
        return 8;
    double k_=k;
    long sum_k=sum_func(round((k_*k_+k_)/2));
    long sum_k_1=sum_func(round((k_*k_-k_)/2));
    return (sum_k-sum_k_1);
}

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