int generateRarityLevel(float factor)
{
    static const float values[] = {3000.f, 1000.f, 200.f, 100.f, 20.f, 5.f, 1.f};
    float dice = 10000.f * rand() / static_cast<float>(RAND_MAX);
    float t = 0.f;
    for(int i=0; i<7; ++i)
    {
        float v = values[i] / powf(factor, 6 - i);
        if(v < 1.f) {
            v = 1.f;
        }
        t += 10000.f / v;
        if(dice < t)
        {
            return 6 - i;
        }
    }
    return 0;
}