{"trustable":true,"sections":[{"title":"","value":{"format":"HTML","content":"The art galleries of the new and very futuristic building of the Center for Balkan Cooperation have the form of polygons (not necessarily convex). When a big exhibition is organized, watching over all of the pictures is a big security concern. Your task is that for a given gallery to write a program which finds the surface of the area of the floor, from which each point on the walls of the gallery is visible. On the figure 1. a map of a gallery is given in some co-ordinate system. The area wanted is shaded on the figure 2. \r\u003cbr\u003e\u003ccenter\u003e\u003cimg src\u003d\"CDN_BASE_URL/4f45f42ad50f7027d0a983b507c75fc6?v\u003d1714650341\"\u003e\u003c/center\u003e"}},{"title":"Input","value":{"format":"HTML","content":"The number of tasks T that your program have to solve will be on the first row of the input file. Input data for each task start with an integer N, 5 \u0026lt;\u003d N \u0026lt;\u003d 1500. Each of the next N rows of the input will contain the co-ordinates of a vertex of the polygon ? two integers that fit in 16-bit integer type, separated by a single space. Following the row with the co-ordinates of the last vertex for the task comes the line with the number of vertices for the next test and so on. "}},{"title":"Output","value":{"format":"HTML","content":"For each test you must write on one line the required surface - a number with exactly two digits after the decimal point (the number should be rounded to the second digit after the decimal point)."}},{"title":"Sample","value":{"format":"HTML","content":"\u003ctable class\u003d\u0027vjudge_sample\u0027\u003e\n\u003cthead\u003e\n \u003ctr\u003e\n \u003cth\u003eInput\u003c/th\u003e\n \u003cth\u003eOutput\u003c/th\u003e\n \u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd\u003e\u003cpre\u003e1\r\n7\r\n0 0\r\n4 4\r\n4 7\r\n9 7\r\n13 -1\r\n8 -6\r\n4 -4\u003c/pre\u003e\u003c/td\u003e\n \u003ctd\u003e\u003cpre\u003e80.00\u003c/pre\u003e\u003c/td\u003e\n \u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n"}}]}