Who was Viktor Krum's Headmaster?

The headmaster of Viktor Krums school Durmstrang is Igor Karkaroff. It is believed that Durmstrang is in either Bulgaria or Norway.

Igor Karkaroff was a Death Eater, but in the fourth book/film, he flees from Voldemort and presumably goes into hiding. In the Half Blood Prince, Lupin says that he was found dead with a dark mark hanging over him, which indicates that he was killed by either Voldemort or other Death Eaters.

We are not told who became Headmaster after Karkaroff.

In the film Karkaroff is played by Predrag Bjelac.