#include <bits/stdc++.h>

using namespace std;

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

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