An ancient manuscript describing the location of a buried treasure has been found: ------ A plane terrain with a bed for strawberries and having just two trees (T1 and T2). From the center C of the bed, measuring the straight line to reach T1. Turning ninety degrees to the left, and then this same distance is needed to straightly reach a point P. Back to the bed to measure the straight distance to reach T2. Turning ninety degrees to the right, and then this same distance is needed to straightly reach the point Q. The treasure is buried down the midpoint of PQ. ------ The plane terrain has been found - but there is no bed! Find the treasure as a function depending on the coordinates of T1 and T2.