{"trustable":false,"sections":[{"title":"","value":{"format":"MD","content":"\u003cimg align\u003d\"right\" src\u003d\"CDN_BASE_URL/01c512ad8c76928fbf6834c9c6c4c1b8?v\u003d1672579862\" hspace\u003d\"10\" vspace\u003d\"10\"\u003eMy birthday is coming up and traditionally I\u0027m serving pie. Not just one pie, no, I have a number N of them, of various tastes and of various sizes. F of my friends are coming to my party and each of them gets a piece of pie. This should be one piece of one pie, not several small pieces since that looks messy. This piece can be one whole pie though.\n\u003cbr\u003e\n\u003cbr\u003eMy friends are very annoying and if one of them gets a bigger piece than the others, they start complaining. Therefore all of them should get equally sized (but not necessarily equally shaped) pieces, even if this leads to some pie getting spoiled (which is better than spoiling the party). Of course, I want a piece of pie for myself too, and that piece should also be of the same size.\n\u003cbr\u003e\n\u003cbr\u003eWhat is the largest possible piece size all of us can get? All the pies are cylindrical in shape and they all have the same height 1, but the radii of the pies can be different.\n\n有 $N$ 个圆形蛋糕,$F$ 个朋友和你自己都要吃蛋糕。每个人分到的蛋糕的面积必须是一样的,并且每个人分到的蛋糕必须是一整块(不能是几个碎块拼凑而成,即这一整块蛋糕是从一个圆形蛋糕中切下的完整一块)。求每个人分到的蛋糕的面积最大为多少。"}},{"title":"Input","value":{"format":"MD","content":"One line with a positive integer: the number of test cases. Then for each test case:\u003cul\u003e\u003cli\u003eOne line with two integers N and F with 1 ≤ N, F ≤ 10 000: the number of pies and the number of friends.\u003c/li\u003e\u003cli\u003eOne line with N integers ri with 1 ≤ ri ≤ 10 000: the radii of the pies.\u003c/li\u003e\u003c/ul\u003e\n\n第一行包括一个整数,表示数据组数。对于每组数据:\n\n* 第一行包括 $N, F$($1 \\le N, F \\le 10000$) 两个整数,表示圆形蛋糕数量和朋友数量。\n* 第二行包括 $N$ 个整数 $r_i$($1 \\le r_i \\le 10000$),表示 $N$ 个圆形蛋糕的半径。"}},{"title":"Output","value":{"format":"MD","content":"对于每组数据,输出一个浮点数,表示每人分到的蛋糕面积的最大值。你输出的答案与标准答案之差不能超过 $10^{-3}$。\n\nFor each test case, output one line with the largest possible volume V such that me and my friends can all get a pie piece of size V. The answer should be given as a floating point number with an absolute error of at most 10\u003csup\u003e−3\u003c/sup\u003e."}},{"title":"Sample","value":{"format":"MD","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\u003e3\n3 3\n4 3 3\n1 24\n5\n10 5\n1 4 2 3 4 5 6 5 4 2\u003c/pre\u003e\u003c/td\u003e\n \u003ctd\u003e\u003cpre\u003e25.1327\n3.1416\n50.2655\u003c/pre\u003e\u003c/td\u003e\n \u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n"}}]}