#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>

using namespace std;

//conversion
//------------------------------------------
inline int toInt(string s) { int v; istringstream sin(s); sin >> v; return v; }
template<class T> inline string toString(T x) { ostringstream sout; sout << x; return sout.str(); }

//math
//-------------------------------------------
template<class T> inline T sqr(T x) { return x*x; }

//typedef
//------------------------------------------
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef long long LL;

//container util
//------------------------------------------
#define ALL(a)  (a).begin(),(a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define PB push_back
#define MP make_pair
#define SZ(a) int((a).size())
#define EACH(i,c) for(typeof((c).begin()) i=(c).begin(); i!=(c).end(); ++i)
#define EXIST(s,e) ((s).find(e)!=(s).end())
#define SORT(c) sort((c).begin(),(c).end())

//repetition
//------------------------------------------
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n)  FOR(i,0,n)

//constant
//--------------------------------------------
const double EPS = 1e-10;
const double PI = acos(-1.0);

//debug
#define dump(x)  cerr << #x << " = " << (x) << endl;
#define debug(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << endl;


bool check(string a){
	for (int i = 0; i < a.size(); i++){
		if (a[i] != a[a.size() - 1 - i]){
			return false;
		}
	}
	return true;
}
int main()
{
	string str;
	cin >> str;
	for (int i = 0; i < str.size(); i++){
		if (str[i] != str[str.size() - 1 - i]){
			string tmp = str;
			tmp=tmp.insert(i,1,str[str.size() - 1 - i]);
			if (check(tmp)){
				cout << tmp << endl;
				return 0;
			}
			tmp = str;
			tmp.insert(i + 1, 1,str[str.size() - 1 - i] );
			if (check(tmp)){
				cout << tmp << endl;
				return 0;
			}
			tmp = str;
			tmp.insert(str.size() - 1 - i, 1,str[i] );
			if (check(tmp)){
				cout << tmp << endl;
				return 0;
			}
			tmp = str;
			tmp.insert(str.size() - i, 1,str[i] );
			if (check(tmp)){
				cout << tmp << endl;
				return 0;
			}
			cout << "NA" << endl;
			return 0;
		}
	}
	if (str.size() % 2 == 0){
		str.insert(str.size() / 2, "a");
		cout << str << endl;
	}
	else{
		cout << "NA" << endl;
	}
	return 0;
}