#include <bits/stdc++.h>
using namespace std;
char s[15], st[15][15];
int n, flag;
int main() {
  cin >> s;
  n = strlen(s);
  for (int i = 0; i <= n; i++) {
    for (int j = 0; j < i; j++) st[i][j] = s[j];
    st[i][i] = '.';
    for (int j = i; j < n; j++) st[i][j + 1] = s[j];
    st[i][n + 1] = '\n';
  }
  for (int i = 0; i <= n; i++) {
    flag = i;
    for (int j = 0; j <= n / 2; j++)
      if (st[i][j] != '.' && st[i][n - j] != '.' && st[i][j] != st[i][n - j]) {
        flag = -1;
        break;
      }
    if (flag != -1) break;
  }
  if (flag == -1) {
    cout << "NA" << endl;
  } else {
    for (int i = 0; i <= n; i++)
      if (st[flag][i] == '.') {
        if (n - i == i)
          cout << 'a' << endl;
        else
          cout << st[flag][n - i];
      } else
        cout << st[flag][i];
    cout << endl;
  }
  return 0;
}
