#include <bits/stdc++.h>
int main() {
  int i, j, l, k, t, z = 1, u;
  char s[100], a[100], m[100];
  memset(m, 0, sizeof(m));
  scanf("%s", s);
  l = strlen(s);
  a[1] = 'a';
  for (i = 2; i <= 'z' - 'a' + 2; i++) a[i] = a[i - 1] + 1;
  for (i = 1; a[i] <= 'z'; i++) {
    for (j = 0; j <= l; j++) {
      t = k = 0;
      while (t < j) {
        m[k] = s[t];
        k++;
        t++;
      }
      m[k] = a[i];
      k++;
      while (t < l) {
        m[k] = s[t];
        k++;
        t++;
      }
      for (u = 0; u < (l + 1) / 2; u++)
        if (m[u] != m[l - u]) z = 0;
      if (z) {
        printf("%s\n", m);
        return 0;
      } else {
        z = 1;
        memset(m, 0, sizeof(m));
      }
    }
  }
  printf("NA\n");
  return 0;
}
