ISL 1994 G2

$ABCD$ is a quadrilateral with $BC$ parallel to $AD$ . $M$ is the midpoint of $CD$ , $P$ is the midpoint of $MA$ and $Q$ is the midpoint of $MB$ . The lines $DP$ and $CQ$ meet at $N$ . Prove that $N$ is inside the quadrilateral $ABCD$ .