basic 2 player wordgame

[Baba]

Hi

I am working on a simple wordgame exercise: 2 players form a word by
alternating turns saying a letter, which is added on to the end of the
word fragment.

I am familiar with loops, iterations etc but i need a hint as to how
to approach alternating turns when writing this code?

exercise source:
http://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-00-introduction-to-computer-science-and-programming-fall-2008/assignments/pset5.pdf

thanks
Baba