#include<iostream>
#include<fstream>
#include<sstream>
#include<string>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<ctime>
#include<stack>
#include<queue>
#include<set>
#include<map>
#include<vector>
#include<list>
#include<algorithm>
#include<utility>
#include<complex>
#include<functional>
using namespace std;


#define input_init stringstream ss; string strtoken, token; istringstream is
#define input_line  getline(cin, strtoken);is.str(strtoken);is.clear(istringstream::goodbit)
#define input_token(num) ss.str(""); ss.clear(stringstream::goodbit); getline(is, token, ','); ss << token; ss >> num


int main(void){
	string s;
	cin >> s;
	int n = (int)s.size();
	if (n == 1){
		cout << s << s << endl;
		return 0;
	}
	int l = 0, r = n - 1;
	bool pain = true;
	while(l<r){
		pain &= (s[l] == s[r]);
		l++;r--;
	}
	if (pain){
		s.insert(n / 2, 1, s[n / 2]);
		cout << s << endl;
		return 0;
	}
	l = 0, r = n - 1;
	while (l < r){
		if (s[l] != s[r])break;
		l++; r--;
	}
	string s1 = s;
	string s2 = s;
	s1.insert(l, 1, s[r]);
	s2.insert(r+1, 1, s[l]);
	pain = true;
	l = 0, r = n;
	while (l < r){
		pain &= (s1[l] == s1[r]);
		l++; r--;
	}
	if (pain){
		cout << s1 << endl;
		return 0;
	}
	pain = true;
	l = 0, r = n;
	while (l < r){
		pain &= (s2[l] == s2[r]);
		l++; r--;
	}
	if (pain){
		cout << s2 << endl;
		return 0;
	}
	cout << "NA" << endl;
	return(0);
}