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

class Program
{
    public void Proc()
    {
        Reader.IsDebug = false;
        string str = Reader.ReadLine();
        string ans = this.GetKaibun(str, true);
        if(ans.Length == 0) {
            ans = "NA";
        }
        Console.WriteLine(ans);
    }
    
    private string GetKaibun(string target, bool canIns) {
        int topIdx = 0;
        int bottomIdx = target.Length - 1;
        while (target[topIdx] == target[bottomIdx] && topIdx < bottomIdx)
        {
            topIdx++;
            bottomIdx--;
        }
        if(target.Length == 1) {
            if(canIns) {
                return target + target;
            } else
            {
                return target;
            }
        }
        if(topIdx >= bottomIdx) {
            return target.Substring(0, topIdx) + target[topIdx] + target.Substring(topIdx);
        } else if(!canIns)
        {
            return string.Empty;
        } else
        {
            string mid = target.Substring(topIdx, bottomIdx + 1 - topIdx);
            string tmp1 = this.GetKaibun(mid.Substring(1), false);
            if(tmp1.Length == 0) {
                tmp1 = this.GetKaibun(mid.Substring(0, mid.Length - 1), false);
                if(tmp1.Length > 0) {
                    mid = mid[0] + mid;
                }
            } else
            {
                mid = mid + mid[0];
            }
            if(tmp1.Length > 0) {
                if(topIdx == 0) {
                    return mid;
                } else
                {
                    return target.Substring(0,topIdx) + mid + target.Substring(bottomIdx + 1);
                }
            } else
            {
                return string.Empty;
            }
        }
    }


    public class Reader
    {
        public static bool IsDebug = true;
        private static String PlainInput = @"


abcdba

 
";
        private static System.IO.StringReader Sr = null;
        public static string ReadLine()
        {
            if (IsDebug)
            {
                if (Sr == null)
                {
                    Sr = new System.IO.StringReader(PlainInput.Trim());
                }
                return Sr.ReadLine();
            }
            else
            {
                return Console.ReadLine();
            }
        }
        public static int[] GetInt(char delimiter = ' ', bool trim = false)
        {
            string inptStr = ReadLine();
            if (trim)
            {
                inptStr = inptStr.Trim();
            }
            string[] inpt = inptStr.Split(delimiter);
            int[] ret = new int[inpt.Length];
            for (int i = 0; i < inpt.Length; i++)
            {
                ret[i] = int.Parse(inpt[i]);
            }
            return ret;
        }
    }
    static void Main()
    {
        Program prg = new Program();
        prg.Proc();
    }
}