#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<cctype>
#include<cstdlib>
#include<algorithm>
#include<bitset>
#include<vector>
#include<list>
#include<deque>
#include<queue>
#include<map>
#include<set>
#include<stack>
#include<cmath>
#include<sstream>
#include<fstream>
#include<iomanip>
#include<ctime>
#include<complex>
#include<functional>
#include<climits>
#include<cassert>
#include<iterator>
using namespace std;

string s;
string rev;
int main(){
	cin >> s;
	rev = s;
	reverse(rev.begin(), rev.end());
	if (s == rev){
		if (s.size() % 2){
			for (int i = 0; i < s.size(); i++){
				cout << s[i];
				if (i == s.size() / 2){
					cout << s[i];
				}
			}
			cout << endl;
			return 0;
		}
		else{
			for (int i = 0; i < s.size(); i++){
				cout << s[i];
				if (i == s.size() / 2-1){
					cout << s[i];
				}
			}
			cout << endl;
			return 0;
		}
	}
	else{
		bool ok = false;
		int i = 0;
		int j = s.size()-1;
		int ind = 0;
		char so = 'a';
		bool ng = false;
		while (i < j){
			if (s[i] != s[j]){
				if (ok){
					ng = true;
					break;
				}
				ind = i;
				j--;
				so = s[j+1];
				ok = true;
				continue;
			}
			i++;
			j--;
		}
		if (ng){

		}
		else{
			for (int i = 0; i < s.size(); i++){
				if (ind == i){
					cout << so;
				}
				cout << s[i];
			}
			cout << endl;
			return 0;
		}
	}
	bool ok = false;
	int i = 0;
	int j = s.size() - 1;
	int ind = 0;
	char so = 'a';
	bool ng = false;
	while (i < j){
		if (s[i] != s[j]){
			if (ok){
				ng = true;
				break;
			}
			ind = j;
			i++;
			so = s[i-1];
			ok = true;
			continue;
		}
		i++;
		j--;
	}
	if (ng){
		puts("NA");
		return 0;
	}
	for (int i = 0; i < s.size(); i++){
		cout << s[i];
		if (ind == i){
			cout << so;
		}
	}
	cout << endl;
	return 0;
}