Lights

There are N lights above a road along the X-axis. The i-th light has Xi as its X-coordinate, and it is hung Yi above the road. The i-th light illuminates a triangular area, which is an isosceles triangle and its bottom edge is on the X-axis. The half of the top angle of the triangle is Zi degrees. (See the below figure) You have an aircraft which can fly on a fixed height. Because of some unknown