#include <bits/stdc++.h>
using namespace std;
int main() {
  int i, j, k, m, n;
  char s[20], s1[20];
  gets(s);
  int ll = strlen(s);
  int l = 0, r = ll - 1;
  int flag = 0;
  while (s[l] == s[r] && l < r) {
    l++;
    r--;
  }
  for (int i = r + 1; i < ll; i++) s1[i + 1] = s[i];
  s1[r + 1] = s[l];
  s1[ll + 1] = '\0';
  for (int i = 0; i <= r; i++) s1[i] = s[i];
  l = 0;
  r = ll;
  while (s1[l] == s1[r] && l <= r) {
    l++;
    r--;
  }
  if (l >= r) {
    printf("%s\n", s1);
    return 0;
  }
  l = 0;
  r = ll - 1;
  while (s[l] == s[r] && l < r) {
    l++;
    r--;
  }
  for (int i = l; i < ll; i++) s1[i + 1] = s[i];
  s1[l] = s[r];
  for (int i = 0; i < l; i++) s1[i] = s[i];
  s1[ll + 1] = '\0';
  l = 0;
  r = ll;
  while (s1[l] == s1[r] && l <= r) {
    l++;
    r--;
  }
  if (l >= r)
    printf("%s\n", s1);
  else
    printf("NA\n");
  return 0;
}
