#include <bits/stdc++.h>
using namespace std;
int main() {
  string s, s1, s2;
  cin >> s;
  int n = s.length();
  int state = 1;
  for (int i = 0; i < n && state; i++) {
    if (s[i] != s[n - 1 - i]) {
      s1 = s;
      string ss1 = "";
      ss1 += s[n - 1 - i];
      s1.insert(i, ss1);
      s2 = s;
      string ss2 = "";
      ss2 += s[i];
      s2.insert(n - i, ss2);
      state = 0;
    }
  }
  if (state) {
    string ss = "";
    ss += s[n / 2];
    s.insert(n / 2, ss);
    cout << s;
    return 0;
  }
  bool b;
  b = 1;
  for (int i = 0; i <= n && b; i++) b &= (s1[i] == s1[n - i]);
  if (b) state = 1;
  b = 1;
  for (int i = 0; i <= n && b; i++) b &= (s2[i] == s2[n - i]);
  if (b) state = 2;
  if (state == 1)
    cout << s1;
  else if (state == 2)
    cout << s2;
  else
    cout << "NA";
  return 0;
}
