#define _USE_MATH_DEFINES
#include <algorithm>
#include <cstdio>
#include <functional>
#include <iostream>
#include <cfloat>
#include <climits>
#include <cstring>
#include <cmath>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <time.h>
#include <vector>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> i_i;
typedef pair<ll, int> ll_i;
typedef pair<double, int> d_i;
typedef pair<ll, ll> ll_ll;
typedef pair<double, double> d_d;
struct edge { int u, v; ll w; };

ll MOD = 1000000007;
ll _MOD = 1000000009;
double EPS = 1e-10;

bool parindoromu(string& s) {
	int n = s.length();
	for (int i = 0, j = n - 1; i < j; i++, j--)
		if (s[i] != s[j])
			return false;
	return true;
}

int main() {
	string s; cin >> s;
	int n = s.length();
	for (int i = 0, j = n - 1; i < j; i++, j--)
		if (s[i] != s[j]) {
			string t = s;
			t.insert(t.begin() + i, s[j]);
			if (parindoromu(t)) {
				cout << t << endl;
				return 0;
			}
			string u = s;
			u.insert(u.begin() + j + 1, s[i]);
			if (parindoromu(u)) {
				cout << u << endl;
				return 0;
			}
			cout << "NA" << endl;
			return 0;
		}
	s.insert(s.begin() + n / 2, s[n / 2]);
	cout << s << endl;
}