#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:100000000000,100000000000")
const long long INF = 1000000007;
const double cp = 2 * asin(1.0);
const double eps = 1e-9;
const long long mod = 1000000007;
using namespace std;
int main() {
  cin.tie(NULL);
  ios_base::sync_with_stdio(false);
  string s, ans;
  bool ok = false;
  cin >> s;
  for (char q = 'a'; q <= 'z'; q++) {
    string h;
    for (int(i) = 0; (i) < (s.size() + 1); i++) {
      h = "";
      for (int(j) = 0; (j) < (i); j++) h += s[j];
      h += q;
      if (i != s.size())
        for (int(j) = (i); (j) <= (s.size() - 1); j++) h += s[j];
      string t = h;
      reverse((t).begin(), (t).end());
      if (t == h) {
        return cout << t, 0;
        ans = t, ok = true;
      }
    }
  }
  if (!ok)
    cout << "NA";
  else
    cout << ans;
  return 0;
}
