{"trustable":true,"sections":[{"title":"","value":{"format":"HTML","content":"An undirected graph is a set V of vertices and a set of E∈{V*V} edges.An undirected graph is connected if and only if for every pair (u,v) of vertices,u is reachable from v.\r\u003cbr\u003eYou are to write a program that tries to calculate the number of different connected undirected graph with n vertices.\r\u003cbr\u003eFor example,there are 4 different connected undirected graphs with 3 vertices.\r\u003cbr\u003e\u003ccenter\u003e\u003cimg src\u003d\"CDN_BASE_URL/6cf5433dd1e316c2dbfbb67f3c18c209?v\u003d1726529510\"\u003e\u003c/center\u003e\r\u003cbr\u003e"}},{"title":"Input","value":{"format":"HTML","content":"The input contains several test cases. Each test case contains an integer n, denoting the number of vertices. You may assume that 1\u0026lt;\u003dn\u0026lt;\u003d50. The last test case is followed by one zero."}},{"title":"Output","value":{"format":"HTML","content":"For each test case output the answer on a single line."}},{"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\n2\r\n3\r\n4\r\n0\r\n\u003c/pre\u003e\u003c/td\u003e\n \u003ctd\u003e\u003cpre\u003e1\r\n1\r\n4\r\n38\r\n\u003c/pre\u003e\u003c/td\u003e\n \u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n"}}]}