#include <bits/stdc++.h>

using namespace std;

long long sumOfGroup(int k) {
    // Return the sum of the elements of the k'th group.
    long long be=k,ans=0;
    be*=(be-1);
    be++;
    while(k--)
    {
        ans+=be;
        be+=2;
    }
    return ans;
}

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