{"trustable":false,"sections":[{"title":"","value":{"format":"MD","content":"“回文串”是一个正读和反读都一样的字符串,比如“level”或者“noon”等等就是回文串,你的任务就是在一个字符串里面,找到一个子串,这个子串是回文串,而且是当中最长的一个"}},{"title":"Input","value":{"format":"MD","content":"输入就一行,一个长度不超过1000的字符串,只包含英文大小写"}},{"title":"Output","value":{"format":"MD","content":"输出最长的回文字符串,如果有多个最长的,就输出**最先出现**的"}},{"title":"Sample Input","value":{"format":"MD","content":"abaca"}},{"title":"Sample Output","value":{"format":"MD","content":"aba"}},{"title":"Sample Input","value":{"format":"MD","content":"Kazak"}},{"title":"Sample Output","value":{"format":"MD","content":"aza"}}]}