#include <bits/stdc++.h>
#define rep(i, a) for (int i = 0; i < (a); i++)
#define rep2(i, a, b) for (int i = (a); i < (b); i++)
using namespace std;
typedef long long ll;
const ll inf = 1e9;
const ll mod = 1e9 + 7;

bool pal(string s) {
    rep (i, s.length()) {
        if (s[i] != s[s.length() - i - 1]) {
            return false;
        }
    }
    return true;
}

int main() {
    string s;
    cin >> s;

    string t = s;
    reverse(t.begin(), t.end());

    int pos = s.length() / 2;

    rep (i, s.length()) {
        if (s[i] != t[i]) {
            pos = i;
            break;
        }
    }

    string ansA = t;
    string ansB = t;

    ansA.insert(pos, string(1, ansA[ansA.length() - pos - 1]));
    ansB.insert(ansB.length() - pos, string(1, ansB[pos]));

    if (pal(ansA)) {
        cout << ansA << endl;
    } else if (pal(ansB)) {
        cout << ansB << endl;
    } else {
        cout << "NA" << endl;
    }
}