Area of Rectangles

Given n rectangles, your task is to determine the total area of their union. Input The first line has an integer n: the number of rectangles. After that, there are n lines describing the rectangles. Each line has four integers x_1, y_1, x_2 and y_2: a rectangle begins at point (x_1,y_1) and ends at point (x_2,y_2). Output Print the total area covered by the rectangles. Constraints - 1 \le n