{"trustable":false,"sections":[{"title":"","value":{"format":"HTML","content":"给定平面上n个点的坐标,它们组成了一个凸多边形(乱序),顺序输出每个定点的坐标\n保证第一个点一定是(0, 0)\n3\u003c\u003dn\u003c\u003d50; -999\u003c\u003dx_i\u003c\u003d999"}},{"title":"Input","value":{"format":"HTML","content":"\n \u003cdiv class\u003d\"ptx\" lang\u003d\"en-US\"\u003e\n The input lists the vertices of a closed convex polygon in the plane. The number of lines in the input will be at least three but no more than 50. Each line contains the x and y coordinates of one vertex. Each x and y coordinate is an integer in the range -999..999. The vertex on the first line of the input file will be the origin, i.e., x \u003d 0 and y \u003d 0. Otherwise, the vertices may be in a scrambled order. Except for the origin, no vertex will be on the x-axis or the y-axis. No three vertices are colinear. \n \u003c/div\u003e"}},{"title":"Output","value":{"format":"HTML","content":"\n \u003cdiv class\u003d\"ptx\" lang\u003d\"en-US\"\u003e\n The output lists the vertices of the given polygon, one vertex per line. Each vertex from the input appears exactly once in the output. The origin (0,0) is the vertex on the first line of the output. The order of vertices in the output will determine a trip taken along the polygon\u0027s border, in the counterclockwise direction. The output format for each vertex is (x,y) as shown below. \n \u003c/div\u003e"}},{"title":"Sample Input","value":{"format":"HTML","content":"\u003cpre class\u003d\"sio\"\u003e0 0\n70 -50\n60 30\n-30 -50\n80 20\n50 -60\n90 -20\n-30 -40\n-10 -60\n90 10\n\u003c/pre\u003e"}},{"title":"Sample Output","value":{"format":"HTML","content":"\u003cpre class\u003d\"sio\"\u003e(0,0)\n(-30,-40)\n(-30,-50)\n(-10,-60)\n(50,-60)\n(70,-50)\n(90,-20)\n(90,10)\n(80,20)\n(60,30)\n\u003c/pre\u003e"}}]}