#include <bits/stdc++.h>
using namespace std;
string pal(string s) {
  int l = s.length();
  if (l == 0) return "a";
  if (l == 1) return s + s;
  return s[0] + pal(s.substr(1, l - 2)) + s[0];
}
bool ispal(string s) {
  if (s.length() < 2) return true;
  int l = s.length();
  if (s[0] == s[l - 1]) return ispal(s.substr(1, l - 2));
  return false;
}
int main() {
  string s;
  cin >> s;
  string temp = s, residue = "";
  bool p = true;
  while (temp.length() > 1) {
    int l = temp.length();
    if (temp[0] == temp[l - 1]) {
      residue = temp[0] + residue;
      temp = temp.substr(1, l - 2);
    } else {
      p = false;
      break;
    }
  }
  if (p)
    cout << pal(s) << endl;
  else {
    if (ispal(temp + temp[0])) {
      temp = temp + temp[0];
      while (residue.length() > 0) {
        temp = residue[0] + temp + residue[0];
        residue = residue.substr(1);
      }
      cout << temp << endl;
    } else if (ispal(temp[temp.length() - 1] + temp)) {
      temp = temp[temp.length() - 1] + temp;
      while (residue.length() > 0) {
        temp = residue[0] + temp + residue[0];
        residue = residue.substr(1);
      }
      cout << temp << endl;
    } else
      cout << "NA\n";
  }
}
