#include <iostream>

using namespace std;

int a, d, n, sum, i, mSum;


unsigned recourse(int a, int d, int n) {
    sum = a;
    if (i < n) {

        i++;
        sum = sum + (i * d);
        return recourse(sum, d, n);

    } else {

        return sum;

    }

}

int main() {

    mSum = 0;
    i = 0;
    cout << recourse(0, 2, 3);

    return 0;
}