#include <bits/stdc++.h>
using namespace std;
int main() {
  string s;
  cin >> s;
  int pntr = s.size() - 1;
  char c;
  for (int i = 0; i < s.size() / 2; i++) {
    if (s[i] != s[pntr]) {
      bool b = true;
      int pntr2 = pntr;
      for (int j = i + 1; j < (s.size() + 1) / 2; j++)
        if (s[j] != s[pntr2]) {
          b = false;
        } else
          pntr2--;
      if (b) {
        c = s[i];
        for (int j = 0; j < s.size(); j++) {
          cout << s[j];
          if (j == pntr) cout << c;
        }
        cout << endl;
        return 0;
      }
      pntr2 = pntr - 1;
      b = true;
      for (int j = i; j < (s.size() + 1) / 2; j++)
        if (s[j] != s[pntr2]) {
          b = false;
        } else
          pntr2--;
      if (b) {
        c = s[pntr];
        for (int j = 0; j < s.size(); j++) {
          if (j == i) cout << c;
          cout << s[j];
        }
        cout << endl;
        return 0;
      }
      cout << "NA" << endl;
      return 0;
    } else
      pntr--;
  }
  if (s.size() % 2) {
    for (int i = 0; i < s.size(); i++)
      if (i == (s.size()) / 2)
        cout << s[i] << s[i];
      else
        cout << s[i];
    cout << endl;
  } else {
    for (int i = 0; i < s.size(); i++)
      if (i == (s.size() / 2))
        cout << "a" << s[i];
      else
        cout << s[i];
    cout << endl;
  }
}
