{"trustable":false,"sections":[{"title":"","value":{"format":"HTML","content":"\n \u003cdiv class\u003d\"ptx\" lang\u003d\"en-US\"\u003e\n \u003cdiv\u003e\n \u003cp\u003e给定长度为N(1≤N≤2000)的字符串S,要构造一个长度为N的字符串T。期初,T是一个空串,随后反复进行下列任意操作。\u003c/p\u003e\n \u003cp\u003e·从S的头部删除一个字符,加到T的尾部\u003c/p\u003e\n \u003cp\u003e·从S的尾部删除一个字符,加到T的尾部\u003c/p\u003e\n \u003cp\u003e目标是要构造字典序尽可能小的字符串\u003c/p\u003e\n \n \u003c/div\u003e\n \u003c/div\u003e"}},{"title":"提示","value":{"format":"HTML","content":"\u003cimg src\u003dhttp://thyrsi.com/t6/652/1546962200x2372231839.bmp /\u003e"}},{"title":"Input","value":{"format":"HTML","content":"\n \u003cdiv class\u003d\"ptx\" lang\u003d\"en-US\"\u003e\n \u003cp\u003e· Line 1: 一个整数(integer): \u003ci\u003eN\u003c/i\u003e\u003cbr\u003e· Lines 2~\u003ci\u003eN \u003c/i\u003e +1: Line \u003ci\u003ei\u003c/i\u003e+1 contains a single initial (\u0027A\u0027..\u0027Z\u0027) of the string in the \u003ci\u003ei\u003c/i\u003eth position in the original line\u003c/p\u003e\n \u003c/div\u003e"}},{"title":"Output","value":{"format":"HTML","content":"\n \u003cdiv class\u003d\"ptx\" lang\u003d\"en-US\"\u003e\n \u003cp\u003e输出时每行最多80个字符\u003c/p\u003e\n \u003c/div\u003e"}},{"title":"Sample Input","value":{"format":"HTML","content":"\u003cpre class\u003d\"sio\"\u003e6\nA\nC\nD\nB\nC\nB\u003c/pre\u003e"}},{"title":"Sample Output","value":{"format":"HTML","content":"\u003cpre class\u003d\"sio\"\u003eABCBCD\u003c/pre\u003e"}}]}