#include <cstdio>
#include <iostream>
#include <sstream>
#include <fstream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <string>
#include <vector>
#include <list>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <bitset>
#include <numeric>
#include <limits>
#include <climits>
#include <cfloat>
#include <functional>
using namespace std;

bool check(const string& s)
{
    string t = s;
    reverse(t.begin(), t.end());
    return s == t;
}

int main()
{
    string s;
    cin >> s;
    int n = s.size();

    int i = 0;
    while(i < n / 2 && s[i] == s[n-1-i])
        ++ i;

    if(i < n / 2){
        string t = s;
        t.insert(t.begin() + i, s[n-1-i]);
        if(check(t)){
            cout << t << endl;
            return 0;
        }
        t = s;
        t.insert(t.begin() + n - i, s[i]);
        if(check(t)){
            cout << t << endl;
            return 0;
        }
    }
    else if(n % 2 == 0){
        s.insert(s.begin() + n / 2, 'a');
        cout << s << endl;
        return 0;
    }
    else{
        s.insert(s.begin() + n / 2, s[n/2]);
        cout << s << endl;
        return 0;
    }

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