The normal at the point $p({\mathrm{ap}}^2, 2\mathrm{ap})$ meets the parabaloa ${\mathrm{y}}^2=4\mathrm{ax}$ again at $q({\mathrm{aq}}^2 , 2\mathrm{aq})$ such that the lines joining the origin to $p$ and $q$ are at right angle then $p^2$=