//yukicoder@cpp17

#include <iostream>
#include <iomanip>

#include <algorithm>

#include <cmath>
#include <cctype>
#include <climits>
#include <cassert>

#include <string>
#include <vector>
#include <set>
#include <stack>
#include <queue>
#include <map>

#include <random>

#include <bitset>

#include <complex>

#include <utility>

#include <numeric>

#include <functional>


using namespace std;
using ll = long long;
using P = pair<ll,ll>;


const ll MOD = 998244353;
const ll MODx = 1000000007;
const int INF = (1<<30)-1;
const ll LINF = (1LL<<62LL)-1;
const double EPS = (1e-10);


P ar4[4] = {{0,1},{0,-1},{1,0},{-1,0}};
P ar8[8] = {{-1,-1},{-1,0},{-1,1},{0,-1},{0,1},{1,-1},{1,0},{1,1}};


template <typename T> vector<T> make_vector(size_t a, T b) { return vector<T>(a, b); }
template <typename... Ts> auto make_vector(size_t a, Ts... ts) { return vector<decltype(make_vector(ts...))>(a, make_vector(ts...)); }
 
/*
確認ポイント
cout << fixed << setprecision(n) << 小数計算//n桁の小数表記になる

計算量は変わらないが楽できるシリーズ
min(max)_element(iter,iter)で一番小さい(大きい)値のポインタが帰ってくる
count(iter,iter,int)でintがiterからiterの間にいくつあったかを取得できる
*/

/* comment outed because can cause bugs
__attribute__((constructor))
void initial() {
  cin.tie(0);
  ios::sync_with_stdio(false);
}
*/

bool isP(string s){
  for(int i = 0; s.size()/2 > i; i++){
    if(s[i] != s[s.size()-i-1])return false;
  }
  return true;
}

int main(){
  string s;cin>>s;
  if(s.size()%2 == 1){
    string ns = s.substr(0,s.size()/2) + s[s.size()/2] + s.substr(s.size()/2,s.size()-s.size()/2);
    if(isP(ns)){
      cout << ns << endl;
      return 0;
    }
    int l = s.size()/2-1;
    int r = s.size()/2;
    while(r != s.size()){
      if(l == -1 || s[l] != s[r]){
        ns = s.substr(0,l+1) + s[r] + s.substr(l+1, s.size()-(l+1));
        if(isP(ns)){
          cout << ns << endl;
          return 0;
        }
        break;
      }
      l--;r++;
    }

    l = s.size()/2;
    r = s.size()/2+1;
    while(l >= 0){
      if(r == s.size() || s[l] != s[r]){
        ns = s.substr(0,r) + s[l] + s.substr(r, s.size()-(r));
        if(isP(ns)){
          cout << ns << endl;
          return 0;
        }
        break;
      }
      l--;r++;
    }

    cout << "NA" << endl;
  }else{
    string ns = s.substr(0, s.size()/2) + "a" + s.substr(s.size()/2, s.size()-(s.size()/2));
    if(isP(ns)){
      cout << ns << endl;
      return 0;
    }
    int l = s.size()/2-1;
    int r = s.size()/2-1;
    while(r != s.size()){
      if(l == -1 || s[l] != s[r]){
        ns = s.substr(0,l+1) + s[r] + s.substr(l+1, s.size()-(l+1));
        if(isP(ns)){
          cout << ns << endl;
          return 0;
        }
        break;
      }
      l--;r++;
    }

    l = s.size()/2;
    r = s.size()/2;
    while(l >= 0){
      if(r == s.size() || s[l] != s[r]){
        ns = s.substr(0,r) + s[l] + s.substr(r, s.size()-(r));
        if(isP(ns)){
          cout << ns << endl;
          return 0;
        }
        break;
      }
      l--;r++;
    }
    cout << "NA" << endl;
  }
  return 0;
}