#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cmath>
#include<cctype>
#include<math.h>
#include<string>
#include<string.h>
#include<stack>
#include<queue>
#include<vector>
#include<utility>
#include<set>
#include<map>
#include<stdlib.h>
#include<iomanip>

using namespace std;

#define ll long long
#define ld long double
#define EPS 0.0000000001
#define INF 1e9
#define LINF (ll)INF*INF
#define MOD 1000000007
#define rep(i,n) for(int i=0;i<(n);i++)
#define loop(i,a,n) for(int i=a;i<(n);i++)
#define all(in) in.begin(),in.end()
#define shosu(x) fixed<<setprecision(x)

#define int ll //!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

typedef vector<int> vi;
typedef vector<string> vs;
typedef pair<int,int> pii;
typedef vector<pii> vp;

int gcd(int a, int b){
    if(b==0) return a;
    return gcd(b,a%b);
}
int lcm(int a, int b){
    return a*b/gcd(a,b);
}

string s;
int n;

bool f(int l,int r){//s[l…r]が回文かどうか判定する
    int i = 0;
    while(l+i <= r-i){
        if(s[l+i] != s[r-i])return false;
        i++;
    }
    return true;
}
// s: … i … n-1-i …
signed main(void) {
    cin >> s;
    n = s.size();
    rep(i,n)if(s[i] != s[n-1-i]){
        if(f(i,n-1-i-1)){
            rep(j,n){
                if(j == i)cout << s[n-1-i];
                cout << s[j];
            }
            cout << endl;
            return 0;
        }
        if(f(i+1,n-1-i)){
            rep(j,n){
                if(j == n-i)cout << s[i];
                cout << s[j];
            }
            if(i == 0)cout << s[0];
            cout << endl;
            return 0;
        }
        cout << "NA" << endl;
        return 0;
    }
    rep(i,n){
        if(2*i == n)cout << s[i];
        if(n%2 && i == n/2)cout << s[i];
        cout << s[i];
    }
    cout << endl;
}