int main()
{
    int x = 5;
    float sum = x;
    for (int i = 2;; i += 2) {
        sum += (-1)*x*x / (i*(i + 1));
    //  cout << i << " " << sum << endl;
        if (sum <= 5)
            break;
    }
    cout << typeid(sum).name();

    system("pause");
    return 0;
}