#include <bits/stdc++.h>
using namespace std;
inline int read() {
  int x = 0, f = 1;
  char c = getchar();
  for (; !isdigit(c); c = getchar())
    if (c == '-') f = -1;
  for (; isdigit(c); c = getchar()) x = x * 10 + c - '0';
  return x * f;
}
const int MAXN = 200010;
char str[MAXN + 1], S[MAXN + 1];
int main() {
  scanf("%s", str + 1);
  int N = strlen(str + 1);
  for (int i = 0; i <= N; i++)
    for (char c = 'a'; c <= 'z'; c++) {
      int top = 0;
      for (int j = 1; j <= i; j++) S[++top] = str[j];
      S[++top] = c;
      for (int j = i + 1; j <= N; j++) S[++top] = str[j];
      bool flag = 1;
      for (int j = 1; j <= top; j++)
        if (S[j] != S[top - j + 1]) {
          flag = 0;
          break;
        }
      if (flag) {
        for (int j = 1; j <= top; j++) printf("%c", S[j]);
        printf("\n");
        return 0;
      }
    }
  printf("NA\n");
  return 0;
}
