#include <bits/stdc++.h>
using namespace std;
bool plaindrome(string s) {
  for (int i = 0, j = s.size() - 1; i < s.size() / 2; i++, j--) {
    if (s[i] != s[j]) return false;
  }
  return true;
}
int main() {
  ios_base::sync_with_stdio(false);
  cout.tie(NULL);
  cin.tie(NULL);
  ;
  string s;
  cin >> s;
  string pos1, pos2;
  if (s.size() == 1)
    cout << s << s;
  else {
    if (plaindrome(s)) {
      string x = "";
      x += s[(s.size() / 2)];
      s.insert((s.size() / 2), x);
      cout << s;
    } else {
      int i, j;
      for (i = 0, j = s.size() - 1; i < s.size() / 2; i++, j--) {
        if (s[i] != s[j]) {
          pos1 = s[i], pos2 = s[j];
          break;
        }
      }
      string temp1 = s, temp2 = s, temp3 = s, temp4 = s;
      temp1.insert(i, pos2);
      temp2.insert(i + 1, pos2);
      temp3.insert(j, pos1);
      temp4.insert(j + 1, pos1);
      if (plaindrome(temp1))
        cout << temp1;
      else if (plaindrome(temp2))
        cout << temp2;
      else if (plaindrome(temp3))
        cout << temp3;
      else if (plaindrome(temp4))
        cout << temp4;
      else
        cout << "NA";
    }
  }
}
