#include <bits/stdc++.h>

using namespace std;



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

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