{"trustable":true,"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":"\u003cp\u003eYour first mission is to find the password of the Martian database. To achieve this, your best secret agents have already discovered the following facts:\u003c/p\u003e\u003cul\u003e \u003cli\u003e The password is a substring of a given string composed of a sequence of non-decreasing digits \u003c/li\u003e\u003cli\u003e The password is as long as possible \u003c/li\u003e\u003cli\u003e The password is always a palindrome \u003c/li\u003e\u003c/ul\u003e\u003cp\u003eA palindrome is a string that reads the same backwards. \u003cspan class\u003d\"tex-font-style-tt\"\u003eracecar\u003c/span\u003e, \u003cspan class\u003d\"tex-font-style-tt\"\u003ebob\u003c/span\u003e, and \u003cspan class\u003d\"tex-font-style-tt\"\u003enoon\u003c/span\u003e are famous examples.\u003c/p\u003e\u003cp\u003eGiven those facts, can you find all possible passwords of the database?\u003c/p\u003e"}},{"title":"Input","value":{"format":"HTML","content":"\u003cp\u003eThe first line contains \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003en\u003c/i\u003e\u003c/span\u003e, the length of the input string (\u003cspan class\u003d\"tex-span\"\u003e1 ≤ \u003ci\u003en\u003c/i\u003e ≤ 10\u003csup class\u003d\"upper-index\"\u003e5\u003c/sup\u003e\u003c/span\u003e). \u003c/p\u003e\u003cp\u003eThe next line contains a string of length \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003en\u003c/i\u003e\u003c/span\u003e. Every character of this string is a digit. \u003c/p\u003e\u003cp\u003eThe digits in the string are in non-decreasing order.\u003c/p\u003e"}},{"title":"Output","value":{"format":"HTML","content":"\u003cp\u003eOn the first line, print the number of possible passwords, \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003ek\u003c/i\u003e\u003c/span\u003e. \u003c/p\u003e\u003cp\u003eOn the next \u003cspan class\u003d\"tex-span\"\u003e\u003ci\u003ek\u003c/i\u003e\u003c/span\u003e lines, print the possible passwords in alphabetical order.\u003c/p\u003e"}},{"title":"Examples","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\u003e8\n34456788\n\u003c/pre\u003e\u003c/td\u003e\n \u003ctd\u003e\u003cpre\u003e2\n44\n88\n\u003c/pre\u003e\u003c/td\u003e\n \u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n"}},{"title":"","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\n0\n\u003c/pre\u003e\u003c/td\u003e\n \u003ctd\u003e\u003cpre\u003e1\n0\n\u003c/pre\u003e\u003c/td\u003e\n \u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n"}},{"title":"Note","value":{"format":"HTML","content":"\u003cp\u003eYou can easily convert a digit encoded as a character to an integer: \u003c/p\u003e\u003cp\u003e\u003cspan class\u003d\"tex-font-style-tt\"\u003e(int)(\u00271\u0027 - \u00270\u0027)\u003c/span\u003e will give you \u003cspan class\u003d\"tex-span\"\u003e1\u003c/span\u003e for instance, in C++ or Java.\u003c/p\u003e\u003cp\u003e\u003cspan class\u003d\"tex-font-style-tt\"\u003eint(\u00274\u0027 - \u00270\u0027)\u003c/span\u003e will give you \u003cspan class\u003d\"tex-span\"\u003e4\u003c/span\u003e in Python.\u003c/p\u003e"}}]}