How to extract the verices from contour matrix those satisfy a condition

Hi,

I have a contour matrix for concentric ellipses. I want to extract the vertices which satisfy particular condition. Let's say I want to extract the vertices whose x coordinates are lesser than -100 and y coordinates are greater than zero. As the contours are ellipses I have repeated x and y coordinates which makes it a bit complicated to extract the coordinates. But anyway I want to extract the vertex pairs whose x coordinate is lesser than -100 and y coordinate greater than zero.

Thanks in advance.