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

#define DEBUG(x) cout<<#x<<": "<<x<<endl;
#define DEBUG_VEC(v) cout<<#v<<":";for(int i=0;i<v.size();i++) cout<<" "<<v[i]; cout<<endl

typedef long long ll;
#define vi vector<int>
#define vl vector<ll>
#define vii vector< vector<int> >
#define vll vector< vector<ll> >
#define vs vector<string>
#define pii pair<int,int>
#define pis pair<int,string>
#define psi pair<string,int>
#define pll pair<ll,ll>
const int inf = 1000000001;
const ll INF = 1e18 * 4;
#define MOD 1000000007
#define mod 1000000009
#define pi 3.14159265358979323846
#define Sp(p) cout<<setprecision(15)<<fixed<<p<<endl;
int dx[4] = { 1,0,-1,0 }, dy[4] = { 0,1,0,-1 };
int dx2[8] = { 1,1,0,-1,-1,-1,0,1 }, dy2[8] = { 0,1,1,1,0,-1,-1,-1 };

int main() {
	string s;
	cin >> s;
	int n = s.size(), i, j;
	int left = 0, right = n - 1;
	string s2 = s, s3 = s;
	bool flag = true;
	while (left < right) {
		if (s[left] == s[right]) {
			left++; right--;
		}
		else {
			s2.insert(s2.begin() + left, s[right]);
			s3.insert(s3.begin() + right + 1, s[left]);
			flag = false;
			break;
		}
	}
	if (flag) {
		s.insert(s.begin() + n / 2, s[n / 2]);
		cout << s << endl;
		return 0;
	}
	left = 0; right = n;
	flag = true;
	while (left < right) {
		if (s2[left] == s2[right]) {
			left++; right--;
		}
		else {
			flag = false;
			break;
		}
	}
	if (flag) {
		cout << s2 << endl;
		return 0;
	}

	left = 0; right = n;
	flag = true;
	while (left < right) {
		if (s3[left] == s3[right]) {
			left++; right--;
		}
		else {
			flag = false;
			break;
		}
	}
	if (flag) {
		cout << s3 << endl;
		return 0;
	}
	cout << "NA" << endl;
	return 0;
}