#include <iostream>
#include <algorithm>
using namespace std;

string s;

bool IsPalindrome(string str) {
    bool same = true;
    for (int i = 0; i < str.size(); i++) {
        same &= str[i] == str[str.size() - i - 1];
    }
    return same;
}

void Solve() {
    for (int alpha = 'a'; alpha <= 'z'; alpha++) {
        for (int i = 0; i <= s.size(); i++) {
            s.insert(s.begin() + i, alpha);
            if (IsPalindrome(s)) {
                cout << s << endl;
                return;
            }
            s.erase(s.begin() + i);
        }
    }
    cout << "NA" << endl;
}

int main() {
    cin >> s;

    Solve();

    return 0;
}