//#define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
#define rep(i, n) for(int i=0; i<n; ++i)
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
using namespace std;
using ll = int64_t;
using ld = long double;
using P = pair<int, int>;
using vs = vector<string>;
using vi = vector<int>;
using vvi = vector<vi>;
template<class T> using PQ = priority_queue<T>;
template<class T> using PQG = priority_queue<T, vector<T>, greater<T> >;
const int INF = 0xccccccc;
const ll LINF = 922337203685477580LL;
template<typename T1, typename T2>
inline bool chmax(T1 &a, T2 b) {return a < b && (a = b, true);}
template<typename T1, typename T2>
inline bool chmin(T1 &a, T2 b) {return a > b && (a = b, true);}
template<typename T1, typename T2>
istream &operator>>(istream &is, pair<T1, T2> &p) { return is >> p.first >> p.second;}
template<typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) { return os << p.first << ' ' << p.second;}



//head

int cnt;
string s, rev;

bool dfs(int i, string &s, string &rev, bool used) {
  if(i == s.size()) return true;
  if(s[i] == rev[i]) {
    return dfs(i+1, s, rev, used);
  }
  else {
    cnt++;
    if(used) return false;
    char c = s[i], cd = rev[i];
    int n = s.size();
    string x = s.substr(0, i) + cd + s.substr(i);
    string y = rev.substr(0, n-i) + cd + rev.substr(n-i);
    if(dfs(i+1, x, y, true)) {
      s = x;
      rev = y;
      return true;
    }
    x = s.substr(0, n-i) + c + s.substr(n-i);
    y = rev.substr(0, i) + c + rev.substr(i);
    if(dfs(i+1, x, y, true)) {
      s = x;
      rev = y;
      return true;
    }
    return false;
  }
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cin >> s;
  rev = s;
  reverse(all(s));
  if(!dfs(0, s, rev, false)) {
    cout << "NA" << endl;
  }
  else {
    if(!cnt) {
      if(s.size()&1) {
        s = s.substr(0, s.size()/2) + s[s.size()/2] + s.substr(s.size()/2);
      }
      else {
        s = s.substr(0, s.size()/2) + 'u' + s.substr(s.size()/2);
      }
    }
    cout << s << endl;
  }
}