Help me in solving PYSTRMCQ3 problem

My issue

i did not clearly understand the question and the solution can anyone explain in a simpler way?

My code


Learning course: Strings using Python
Problem Link: CodeChef: Practical coding for everyone

The question says that if the server scores a point he will get 1 point and if the receiver scores a point neither of them gets any point but the receiver will become server and the server will become receiver.
for ex ;- ABB
It is said that initially Alice is server , so
first A scores which means alice will get 1 point (1-0)
second B scores which means Bob will become server and Alice will become receiver (1-0)
thirst B scores again which measn Bob will get one point (1-1)
this way they end up having equal scores.