#include <iostream>
#include <vector>
#include <cmath>
#include <map>
#include <set>
#include <iomanip>
#include <queue>
#include <algorithm>
#include <numeric>
#include <deque>
#include <complex>
#include <cassert>

using namespace std;

bool judge(string &S){
    int N=S.size();

    for (int i=0; i<N/2; i++){
        if (S[i] != S[N-1-i]) return 0;
    }

    return 1;
}

int main(){

    string S, T;
    cin >> S;
    int N = S.size();
    if (judge(S)){
        T = S.substr(0, N/2) + S[N/2] + S.substr(N/2, N/2+1);
        cout << T << endl;
        return 0;
    }
    
    for (int i=0; i<N/2; i++){
        if (S[i] != S[N-1-i]){
            T = S.substr(0, i) + S[N-1-i] + S.substr(i);
            if (judge(T)){
                cout << T << endl;
                return 0;
            }
            T = S.substr(0, N-1-i+1) + S[i] + S.substr(N-1-i+1);
            if (judge(T)){
                cout << T << endl;
                return 0;
            }
            break;
        }
    }

    cout << "NA" << endl;

    return 0;
}