{"trustable":false,"prependHtml":"\u003cstyle type\u003d\u0027text/css\u0027\u003e\n .input, .output {\n border: 1px solid #888888;\n }\n .output {\n margin-bottom: 1em;\n position: relative;\n top: -1px;\n }\n .output pre, .input pre {\n background-color: #EFEFEF;\n line-height: 1.25em;\n margin: 0;\n padding: 0.25em;\n }\n \u003c/style\u003e\n \u003clink rel\u003d\"stylesheet\" href\u003d\"//codeforces.org/s/96598/css/problem-statement.css\" type\u003d\"text/css\" /\u003e\u003cscript\u003e window.katexOptions \u003d { disable: true }; \u003c/script\u003e\n\u003cscript type\u003d\"text/x-mathjax-config\"\u003e\n MathJax.Hub.Config({\n tex2jax: {\n inlineMath: [[\u0027$$$\u0027,\u0027$$$\u0027], [\u0027$\u0027,\u0027$\u0027]],\n displayMath: [[\u0027$$$$$$\u0027,\u0027$$$$$$\u0027], [\u0027$$\u0027,\u0027$$\u0027]]\n }\n });\n\u003c/script\u003e\n\u003cscript type\u003d\"text/javascript\" async src\u003d\"https://mathjax.codeforces.org/MathJax.js?config\u003dTeX-AMS_HTML-full\"\u003e\u003c/script\u003e","sections":[{"title":"","value":{"format":"HTML","content":"给你一个仅仅包含小写字母的字符串s.\u003cbr\u003e\n你可以将某个字母换成另外一个字母,这被称为一次操作.\u003cbr\u003e\n所有的操作完成之后,你可以任意调换其中字母的顺序(不计入操作).\u003cbr\u003e\n你需要用最小的步骤数将所给字符串变成回文串,如果有多种步骤数最小的情况,那么请你输出字典序最小的回文串."}},{"title":"Input","value":{"format":"HTML","content":"输入只有一个,包含一个长度小于等于2*10^5的非空字符串(只包含小写字母)."}},{"title":"Output","value":{"format":"HTML","content":"请你输出符合要求的回文串。"}},{"title":"Examples","value":{"format":"HTML","content":"【样例输入】\u003cbr\u003e\naabcd\u003cbr\u003e\n\u003cbr\u003e\n【样例输出】\u003cbr\u003e\nabcba"}}]}