Two vertical parallel mirrors A and B are separated by $10 \mathrm{~cm}$. A point object $\mathrm{O}$ is placed at a distance of $2 \mathrm{~cm}$ from mirror $\mathrm{A}$. The distance of the second nearest image behind mirror A from the mirror $\mathrm{A}$ is _________ $\mathrm{cm}$.