import std.conv, std.stdio, std.string;
import std.algorithm, std.array, std.bigint, std.container, std.math, std.range, std.regex, std.typecons;
import core.bitop;

class EOFException : Throwable { this() { super("EOF"); } }
string[] tokens;
string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens.popFront; return token; }
int readInt() { return readToken().to!int; }
long readLong() { return readToken().to!long; }
real readReal() { return readToken().to!real; }

void chmin(T)(ref T t, in T f) { if (t > f) t = f; }
void chmax(T)(ref T t, in T f) { if (t < f) t = f; }

int binarySearch(T)(in T[] as, in bool delegate(T) test) { int low = -1, upp = cast(int)(as.length); for (; low + 1 < upp; ) { int mid = (low + upp) >> 1; (test(as[mid]) ? low : upp) = mid; } return upp; }
int lowerBound(T)(in T[] as, in T val) { return as.binarySearch((T a) => (a < val)); }
int upperBound(T)(in T[] as, in T val) { return as.binarySearch((T a) => (a <= val)); }


bool isPalindrome(string s) {
  return (s == s.dup.reverse);
}

int N;
string S;

void main() {
  try {
    for (; ; ) {
      S = readToken();
      N = cast(int)(S.length);
      if (isPalindrome(S)) {
        writeln(S[0 .. N / 2] ~ S[N / 2] ~ S[N / 2 .. N]);
      } else {
        string ans = "NA";
        for (int i = 0, j = N - 1; i < j; ++i, --j) {
          if (S[i] != S[j]) {
            {
              const s = S[0 .. i] ~ S[j] ~ S[i .. N];
              if (isPalindrome(s)) {
                ans = s;
                break;
              }
            }
            {
              const s = S[0 .. j + 1] ~ S[i] ~ S[j + 1 .. N];
              if (isPalindrome(s)) {
                ans = s;
                break;
              }
            }
            break;
          }
        }
        writeln(ans);
      }
    }
  } catch (EOFException e) {
  }
}