#include <bits/stdc++.h>
using namespace std;
bool isPalindrome(string str) {
  int l = 0;
  int h = str.length() - 1;
  while (h > l) {
    if (str[l++] != str[h--]) {
      return false;
    }
  }
  return true;
}
int main() {
  string s, ss, sp;
  cin >> s;
  ss = s, sp = s;
  long long n = s.length();
  if (ss[0] != ss[n - 1]) {
    ss.insert(0, 1, s[n - 1]);
    if (isPalindrome(ss)) {
      cout << ss;
      return 0;
    }
    sp.append(1, sp[0]);
    if (isPalindrome(s)) {
      cout << sp;
      return 0;
    }
  }
  for (long long i = 0; i < n / 2; i++) {
    if (s[i] != s[n - i - 1]) {
      string s1 = s, s2 = s, s3 = s, s4 = s;
      s1.insert(i, 1, s[n - i - 1]);
      if (isPalindrome(s1)) {
        cout << s1;
        return 0;
      }
      s2.insert(n - i, 1, s[i]);
      if (isPalindrome(s2)) {
        cout << s2;
        return 0;
      }
    }
  }
  if (isPalindrome(s) && n % 2 == 0) {
    string t = s;
    t.insert(n / 2, 1, 'a');
    cout << t;
    return 0;
  }
  if (n == 1) {
    cout << s << s;
    return 0;
  }
  if (n % 2 == 1) {
    string t = s;
    t.insert(n / 2, 1, s[n / 2]);
    if (isPalindrome(t)) {
      cout << t;
      return 0;
    }
  }
  cout << "NA";
  return 0;
}
