#include <bits/stdc++.h>

using namespace std;

unsigned long long sumOfGroup(int k) {
    // Return the sum of the elements of the k'th group.
    int i;
    unsigned long long sum=0,start;
    for(i=1;i<k;i++)
        sum += i;
    return k*((sum*2+1)+(k-1));
}

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