#include <bits/stdc++.h>

using namespace std;

long long int sumOfGroup(long long int k) {
   long long int temp=(k*(k+1))/2;
    long long int  sub=temp-k;
    long long int ans=(temp*temp)-(sub*sub);
    return ans;
}

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