A mobile phone company ACMICPC (Advanced Cellular, Mobile, and Internet-Connected Phone Corporation) is planning to set up a collection of antennas for mobile phones in a city called Maxnorm. The company ACMICPC has several collections for locations of antennas as their candidate plans, and now they want to know which collection is the best choice.
For this purpose, they want to develop a computer program to find the coverage of a collection of antenna locations. Each antenna Ai has power ri, corresponding to "radius". Usually, the coverage region of the antenna may be modeled as a disk centered at the location of the antenna (xi, yi) with radius ri. However, in this city Maxnorm such a coverage region becomes the square [xi - ri, xi + ri] x [yi - ri, yi + ri]. In other words, the distance between two points (xp, yp) and (xq, yq) is measured by the max norm max{|xp - xq|, |yp - yq|}, or, the L norm, in this city Maxnorm instead of the ordinary Euclidean norm sqrt((xp - xq)^2 + (yp - yq)^2).
As an example, consider the following collection of 3 antennas
4.0 4.0 3.0
5.0 6.0 3.0
5.5 4.5 1.0
depicted in the following figure

where the i-th row represents xi, yi, ri such that (xi, yi) is the position of the i-th antenna and ri is its power. The area of regions of points covered by at least one antenna is 52.00 in this case.
Write a program that finds the area of coverage by a given collection of antenna locations.