#include <bits/stdc++.h>
using namespace std;
const int N = int(3e6);
char second[22];
int n;
string q, k;
bool check(string k) {
  int i = 0, j = k.size() - 1;
  while (i < j) {
    if (k[i] != k[j]) return 0;
    i++;
    j--;
  }
  return 1;
}
int main() {
  cin >> second;
  n = strlen(second);
  for (int i = 0; i <= n; i++) {
    for (int t = 0; t < 26; t++) {
      k = "";
      for (int j = 0; j < i; j++) {
        k += second[j];
      }
      k += char(t + 'a');
      for (int j = i; j < n; j++) {
        k += second[j];
      }
      if (check(k)) {
        cout << k << endl;
        ;
        return 0;
      }
    }
  }
  cout << "NA";
  return 0;
}
