#include <bits/stdc++.h>
using namespace std;
int main() {
  string S, S1, S2, S11, S21;
  getline(cin, S);
  int N = S.length();
  int i, j, k;
  int t = 0, t3 = 0;
  for (i = 0; i < N; i++) {
    if (S[i] != S[N - i - 1] and t3 == 0) {
      t3 = 1;
      if (S[i + 1] == S[N - i - 1]) {
        t = 1;
        S1 = S;
        S1 += S1[N - 1];
        for (j = N - 1; j > N - i - 1; j--) {
          S1[j + 1] = S1[j];
        };
        S1[N - i] = S1[i];
      }
      if (S[i] == S[N - i - 2]) {
        t = 1;
        S2 = S;
        S2 += S2[N - 1];
        for (j = N - 1; j > i - 1; j--) {
          S2[j + 1] = S2[j];
        };
        S2[i] = S2[N - i];
      }
      if (t == 0) {
        t = 1;
        cout << "NA";
        return 0;
      }
    }
  }
  S11 = S1 + '1';
  S21 = S2 + '1';
  if (t3 == 0) {
    S += S[N - 1];
    for (j = N - 1; j >= (N - 1) / 2; j--) {
      S[j + 1] = S[j];
    };
    cout << S;
    return 0;
  };
  int t1 = 0, t2 = 0, t5 = 0, t6 = 0;
  for (i = 0; i <= N; i++) {
    if (S1[i] != S1[N - i]) {
      t1 = 1;
    }
  }
  for (i = 0; i <= N; i++) {
    if (S2[i] != S2[N - i]) {
      t2 = 1;
    }
  }
  if (t1 == 0 and S11 != "1") {
    cout << S1;
    return 0;
  }
  if (t2 == 0 and S21 != "1") {
    cout << S2;
    return 0;
  }
  cout << "NA";
  return 0;
}
