An algorithm problem

[Sybren Stuvel]

Bo Yang enlightened us with:
> I have writen a python program to slove a problem described as
> below:

Please post again, but then leaving indentation intact, since this is
unreadable.

Sybren
-- 
The problem with the world is stupidity. Not saying there should be a
capital punishment for stupidity, but why don't we just take the
safety labels off of everything and let the problem solve itself? 
                                             Frank Zappa