#include <algorithm>
#include <array>
#include <cstdio>
#include <cstdlib>
#include <cctype>
#include <ostream>
#include<complex>
#include <cmath>
#include <iostream>
#include <stack>
#include <fstream>
#include <queue>
#include <list>
#include <map>
#include <numeric>
#include <set>
#include <sstream>
#include <string>
#include <vector>
#include <string>
using namespace std;
#define REP(i,a,n) for(int i=(a); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define ALLOF(c) (c).begin(), (c).end()
typedef long long ll;



int main()
{
    string s;
    cin >> s;
    bool filled = false;
    rep(i,s.size()/2 - 1) // fill test
    {
        if (s[i] != s[s.size() - 1 - i])
        {
            s.insert(s.size()-i,s.substr(i,1));
            filled = true;
            break;
        }
    }
    if (!filled)
    {
        s.insert(s.size()/2,s.substr(s.size()/2,1));
    }
    rep(i,s.size()) // check
    {
        if (s[i] != s[s.size()- 1 - i])
        {

#ifdef _DEBUG
            cout << s[i] << " " << s[s.size() - 1 - i] << endl;
#endif _DEBUG      

            cout << "NA" << endl;
            return 0;
        }
    }
    cout << s << endl;
    return 0;
}