#include "bits/stdc++.h"
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef vector<int> veci;
typedef vector<string> vecs;
template<class T,class U> using Hash=unordered_map<T,U>;

#define REP(i, a, n) for(ll i = a; i < n; i++)
#define RREP(i, a, n) for(ll i = n-1; i >= a; i--)
#define rep(i, n) REP(i, 0, n)
#define rrep(i, n) RREP(i, 0, n)
#define MD 1000000007

template<class T> T read(){T a;cin >> a;return a;}
template<class T> void read(T& a){cin >> a;}
template<class T> void rarr(T a, int n){for(int i = 0; i < n; i++) {cin >> a[i];}}
template<class T> void write(T a){cout << a << endl;}
template<class T> void writes(vector<T> a, char* c = " "){cout << a[0];for(int i = 1; i < a.size(); i++)cout << c << a[i];cout << endl;;}
void write(double a){cout << fixed << setprecision(12) << a << endl;}
template<class T> void warr(T a, int n, char* c = " "){cout << a[0];for(int i = 1; i < n; i++)cout << c << a[i];cout << endl;}
void split(string s, string delim, veci& result){result.clear();string::size_type pos = 0;while(pos != string::npos){string::size_type p = s.find(delim, pos);if(p == string::npos){result.push_back(atoi(s.substr(pos).data()));break;}else {result.push_back(atoi(s.substr(pos, p - pos).data()));}pos = p + delim.size();}}
void split(string s, string delim, vecs& result){result.clear();string::size_type pos = 0;while(pos != string::npos){string::size_type p = s.find(delim, pos);if(p == string::npos){result.push_back(s.substr(pos));break;}else {result.push_back(s.substr(pos, p - pos));}pos = p + delim.size();}}
ll gcd(ll a, ll b){while(true){ll k = a % b;if(k == 0)return b;a = b;b = k;}}
ll comb(ll n, ll m){ll p=1;m=min(m,n-m);for(ll i=1;i<=m;i++){p*=n-i+1;p/=i;}return p;}
int n;
bool kb(string& s){
    int sz=s.size();
    rep(i,sz/2){
        if(s[i]!=s[sz-i-1])
            return false;
    }
    return true;
}

int main(void)
{
    string s=read<string>();
    n=s.size();
    if(kb(s)){
        if(n%2==0){
            s.insert(n/2,"t");
        }
        else{
            string c;c+=s[n/2];
            s.insert(n/2,c);
        }
        write(s);
        return 0;
    }
    RREP(i,1,n/2){
        if(s[i]==s[n-i])continue;
        string s1=s;string c;c+=s[i];
        s1.insert(n-i,c);
        if(kb(s1)){
            write(s1);
            return 0;
        }
        break;
    }
    RREP(i,0,(n-1)/2){
        if(s[i]==s[n-i-1])continue;
        string s1=s;string c;c+=s[n-i-1];
        s1.insert(i,c);
        if(kb(s1)){
            write(s1);
            return 0;
        }
        break;
    }
    string s1=s+s[0];
    string s2=s[n-1]+s;
    if(kb(s1)){
        write(s1);
        return 0;
    }
    if(kb(s2)){
        write(s2);
        return 0;
    }
    write("NA");
	return 0;
}