What is the fine-grained topic of the following text: Vadim Rogovskiy is a serial entrepreneur who sold his first startup AdCenter in 2014, bootstrapped his next company Clickky, the 11th fastest growing tech company in Europe, to 100+ employees and $13M+ annual revenue, and organizes one of the best tech conferences in Eastern Europe. Only return the topic.
Vadim Rogovskiy's Entrepreneurial Achievements