getE

#include <iostream>
using namespace std;

int getE()
{
    int n, e = 0;
    cout << "n=";cin >> n;
    for (int x = 1; x <= n; x++)
        e += (3 * x - 2);

    return e;
}

int main()
{
    cout << getE();
    return 0;
}