#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <queue>
#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;

typedef long long ll;
typedef unsigned long long ull;

static const double EPS = 1e-8;
static const double PI = 4.0 * atan(1.0);
static const double PI2 = 8.0 * atan(1.0);

#define REP(i,n)	for(int i=0;i<(int)n;++i)
#define ALL(c)		(c).begin(),(c).end()
#define CLEAR(v)	memset(v,0,sizeof(v))
#define MP(a,b)		make_pair((a),(b))
#define ABS(a)		((a)>0?(a):-(a))
#define FOR(i,s,n)	for(int i=s;i<(int)n;++i)

const string NA = "NA";

string s;

int main(int argc, char **argv) {
	cin >> s;
	if (s.length() <= 2) {
		cout << s << s[0] << endl;
		return 0;
	}
	string res;
	REP(i, s.length()) {
		int j = s.length() - 1 - i;
		if (s[i] != s[j]) {
			bool f = false;
			string a = s.substr(i, j - i), b = s.substr(i + 1, j - i);
			REP(k, a.length()) f |= (a[k] != a[a.length() - 1 - k]);
			if (!f) {
				res = s.substr(0, i) + s[j] + a + s[j] + s.substr(j + 1);
				break;
			}
			f = false;
			REP(k, b.length()) f |= (b[k] != b[b.length() - 1 - k]);
			if (!f) {
				res = s.substr(0, i) + s[i] + b + s[i] + s.substr(j + 1);
				break;
			}
			res = NA;
			break;
		}
	}
	if (res == "") {
		cout << s.substr(0, s.length() / 2) << s[s.length() / 2] << s.substr(s.length() / 2) << endl;
	}
	else {
		cout << res << endl;
	}
	return 0;
}