#include <bits/stdc++.h>

using namespace std;

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

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