removal of vinyl on top of vinyl

The kitcen floor of the rental apt. that I am vacanting next week was ugly. Therefore, I placed those sticky vinyl tiles(they sell them at Meijer's) on top of the ugly vinyl floor. Now I need to get the better looking vinyl tiles off of the apt. ugly stuff.
I have been removing them very, very slow by pushing a sharp knife to each tile. But it is very tiring and time consuming.

What are my options?

Thanks!