using System;
using System.Collections.Generic;
using System.Linq;

namespace YukiCoderNo238
{
    class Program
    {
        static void Main()
        {
            string input = LIB.IO.R<string>();
            char[] inputarray = input.ToCharArray();
            int count = inputarray.Count();
            bool flag = false;
            bool ba = false;
            int mem = 0;
            char c = ' ';
            for (int i = 0, j = count - 1; i < count / 2 + count % 2; i++, j--)
            {
                if (inputarray[i] != inputarray[j])
                {
                    if (flag == true)
                    {
                        flag = false;
                        ba = true;
                        for (int k = 0, l = count - 1; k < count / 2; k++, l--)
                        {
                            if (inputarray[k] != inputarray[l])
                            {
                                if (flag == true)
                                {
                                    LIB.IO.W("NA");
                                    LIB.IO.WFLUSH();
                                    return;
                                }
                                else
                                {
                                    flag = true;
                                    mem = k;
                                    c = inputarray[l];
                                    k--;
                                }
                            }
                        }
                    }
                    else
                    {
                        flag = true;
                        mem = j;
                        c = inputarray[i];
                        j++;
                    }
                }
            }
            if (flag == true)
            {
                if (ba == false)
                {
                    LIB.IO.W(new string(inputarray, 0, mem + 1), false);
                    LIB.IO.W(c, false);
                    if (mem < count - 1) { LIB.IO.W(new string(inputarray, mem + 1, count - mem - 1), false); }
                    LIB.IO.W("");
                }
                else
                {
                    LIB.IO.W(new string(inputarray, 0, mem), false);
                    LIB.IO.W(c, false);
                    if (mem < count - 1) { LIB.IO.W(new string(inputarray, mem, count - mem), false); }
                    LIB.IO.W("");
                }
            }
            else
            {
                if ((count % 2) == 0)
                {
                    LIB.IO.W(new string(inputarray, 0, count / 2), false);
                    LIB.IO.W('a', false);
                    LIB.IO.W(new string(inputarray, count / 2, count / 2), false);
                    LIB.IO.W("");
                }
                else
                {
                    if (count == 1)
                    {
                        LIB.IO.W(inputarray[0], false);
                        LIB.IO.W(inputarray[0], false);
                    }
                    else
                    {
                        LIB.IO.W(new string(inputarray, 0, count / 2), false);
                        LIB.IO.W(inputarray[count / 2], false);
                        LIB.IO.W(new string(inputarray, count / 2 , count / 2 + 1), false);
                    }
                    LIB.IO.W("");
                }
            }
            LIB.IO.WFLUSH();
        }
    }
}
namespace LIB
{
    public class IO
    {
        private const int WMAX = 1000;
        private static string WSTRING = "";
        public static T R<T>()
        {
            return (T)(Convert.ChangeType(R(), typeof(T)));
        }
        public static T[] R<T>(char splitter = ' ')
        {
            return R().Split(splitter).Select(v => UTILITY.PARSE<T>(v)).ToArray();
        }
        public static T[] R<T>(int length)
        {

            T[] ret = new T[length];
            for (int i = 0; i < length; i++)
            {
                ret[i] = R<T>();
            }
            return ret;
        }
        public static T[][] R<T>(int length, char splitter = ' ')
        {
            T[][] ret = new T[length][];
            for (int i = 0; i < length; i++)
            {
                ret[i] = R<T>(splitter);
            }
            return ret;
        }
        private static string R()
        {
            return Console.ReadLine();
        }
        public static void W(object value, bool addLineFeed = true)
        {
            WSTRING += UTILITY.PARSE<string>(value);
            if (addLineFeed == true) { WSTRING += "\n"; }
            if (WSTRING.Count() >= WMAX) { WFLUSH(); }
        }
        public static void WFLUSH()
        {
            Console.Write(WSTRING);
            WSTRING = "";
        }
    }
    public class UTILITY
    {
        public static T PARSE<T>(object value)
        {
            return (T)(Convert.ChangeType(value, typeof(T)));
        }
    }
}