An unfair coin with the probability of p to get a head is tossed n times. (n>6).

A success is defined as getting ONLY 4 heads in a row.

So that hhhht is a succes for the first 5 tosses

THHHH is a succes for the last five.

And THHHHT is a success for all the rest.

Let Y be the number of successe in n tosses.

Whats the expectation of Y?

I am truely lost.