# README
Two heads are better than one
An unbiased coin is tossed repeatedly until two consecutive heads are obtained. Suppose these occur on the$(M-1)$th and $M$th toss.
Let $P(n)$ be the probability that $M$ is divisible by $n$. For example, the outcomes HH, HTHH, and THTTHH all count towards $P(2)$, but THH and HTTHH do not.
You are given that $P(2) = \frac{3}{5}$ and $P(3) = \frac{9}{31}$. Indeed, it can be shown that $P(n)$ is always a rational number.
For a prime $p$ and a fully reduced fraction $\frac{a}{b}$, define $Q(\frac{a}{b}, p)$ to be the smallest positive $q$ for which $a \equiv bq (\bmod p)$.
For example $Q(P(2), 109) = Q(\frac{3}{5}, 109) = 66$, because $5\cdot 66 = 330 \equiv 3 (\bmod 109)$ and 66 is the smallest positive such number.
Similarly $Q(P(3), 109) = 46$.
Find $Q(P(10^{18}), 1\ 000\ 000\ 009)$.