Well if you either get head or tail, it's usually considered a pretty successful date overall.
I cant make head or tail of it.. (sorry)
Thanks for the replies guys. I agree the head/tail terms can be a bit confusing. The solution I implemented was as RoyalSchrubber suggests to just walk till you hit (n-4)th element. I have sent an email querying this as dont want them failing anyone else
on this who bothers to read the question properly.