Implicit float conversion warning

When I run the game, I get the following warnings:

[ed@ed algorithm-playground]$ python main.py
pygame 1.9.6
Hello from the pygame community. https://www.pygame.org/contribute.html
libpng warning: Interlace handling should be turned on when using png_read_image
libpng warning: Interlace handling should be turned on when using png_read_image
libpng warning: Interlace handling should be turned on when using png_read_image
libpng warning: Interlace handling should be turned on when using png_read_image
main.py:8: DeprecationWarning: an integer is required (got type float). Implicit conversion to integers using __int__ is deprecated, and may be removed in a future version of Python.
bg.blit(track,a_coords)

While we can't get rid of the libpng issues (they occur in SDL I think), the DeprecationWarning is something we can and should get rid of (why?).

Please fix this warning.