CF505A.Mr. Kitayuta's Gift

Mr. Kitayuta has kindly given you a string s consisting of lowercase English letters. You are asked to insert exactly one lowercase English letter into s to make it a palindrome. A palindrome is a string that reads the same forward and backward. For example, "noon", "testset" and "a" are all palindromes, while "test" and "kitayuta" are not.

You can choose any lowercase English letter, and insert it to any position of s, possibly to the beginning or the end of s. You have to insert a letter even if the given string is already a palindrome.

If it is possible to insert one lowercase English letter into s so that the resulting string will be a palindrome, print the string after the insertion. Otherwise, print "NA" (without quotes, case-sensitive). In case there is more than one palindrome that can be obtained, you are allowed to print any of them.

北谷先生好心地给了您一个由小写英文字母组成的字符串 $s$。您的任务是在 $s$ 中恰好插入一个小写英文字母，使其成为一个回文串。回文串是指正读和反读都相同的字符串。例如，“noon”、“testset”和“a”都是回文串，而“test”和“kitayuta”则不是。

您可以任选一个小写英文字母，并将其插入到 $s$ 的任意位置（包括字符串的开头或结尾）。即使给定的字符串 $s$ 本身已经是回文串，也必须插入一个字母。

如果存在一种方式，通过在 $s$ 中插入一个小写英文字母，使得结果字符串为回文串，则输出插入后的字符串；否则，输出 "NA"（不带引号，区分大小写）。若存在多种可行方案，输出其中任意一种即可。

The only line of the input contains a string s (1 ≤ |s| ≤ 10). Each character in s is a lowercase English letter.

输入仅包含一行，为一个字符串 $s$（$1 \le |s| \le 10$）。字符串 $s$ 中的每个字符均为小写英文字母。

If it is possible to turn s into a palindrome by inserting one lowercase English letter, print the resulting string in a single line. Otherwise, print "NA" (without quotes, case-sensitive). In case there is more than one solution, any of them will be accepted.

如果可以通过插入一个英文小写字母将字符串 s 变为回文串，则在一行中输出所得字符串；否则，输出 "NA"（不带引号，区分大小写）。若存在多个可行解，输出任意一个即可。

For the first sample, insert 'r' to the end of "revive" to obtain a palindrome "reviver".

For the second sample, there is more than one solution. For example, "eve" will also be accepted.

For the third sample, it is not possible to turn "kitayuta" into a palindrome by just inserting one letter.

对于第一个样例，在字符串 “revive” 末尾插入字母 ‘r’，可得到回文串 “reviver”。

对于第二个样例，存在多种可行解。例如，“eve” 同样可被接受。

对于第三个样例，仅通过插入一个字母无法将 “kitayuta” 变为回文串。