Particle Reach VIII

$\textbf{Complete Particle Reach VI First!}$ Consider a particle that performs a random walk on the integers starting at position $0$. At each step, the particle moves from position $i$ to position $i+1$ with probability $p$, while the probability it moves from $i$ to $i-1$ is $1-p$. If $p = 2/3$, find the expected number of steps until the particle reaches $7$. If the answer is infinite, answer $-1$.