#include <bits/stdc++.h>
using namespace std;
int main() {
  string s;
  cin >> s;
  int c = s.size(), n, t, w;
  if (c == 1) {
    s.push_back(s[0]);
    return cout << s, 0;
  }
  n = c, t = c, c /= 2;
  n--;
  t--;
  bool isnot = false;
  for (int i = 0; i < c; ++i)
    if (s[i] != s[n - i]) {
      isnot = true;
      break;
    }
  if (!isnot) {
    char k = s[c];
    s.insert(s.begin() + c, k);
    return cout << s << "\n", 0;
  }
  isnot = false;
  for (int j = 0; j < c; ++j)
    if (s[j] != s[n]) {
      s.insert(s.begin() + (n + 1), s[j]);
      w = n + 1;
      break;
    } else
      n--;
  int v = s.size(), l;
  l = v - 1;
  v /= 2;
  for (int i = 0; i < v; ++i)
    if (s[i] != s[l - i]) {
      isnot = true;
      break;
    }
  if (!isnot) return cout << s << "\n", 0;
  s.erase(s.begin() + w);
  reverse(s.begin(), s.end());
  isnot = false;
  for (int j = 0; j < c; ++j)
    if (s[j] != s[t]) {
      s.insert(s.begin() + (t + 1), s[j]);
      w = t + 1;
      break;
    } else
      t--;
  for (int i = 0; i < v; ++i)
    if (s[i] != s[l - i]) {
      isnot = true;
      break;
    }
  reverse(s.begin(), s.end());
  if (!isnot) return cout << s << "\n", 0;
  cout << "NA\n";
  return 0;
}
