#include <iostream>
using namespace std;

bool isPalin(const string& s){
	const int n = s.size();
	for(int i=0;i<n;i++){
		if(s[i] != s[n-i-1])return false;
	}
	return true;
}

string solve(const string& s){
	const int n = s.size();
	if(isPalin(s)){
		string front = s.substr(0, n / 2);
		string back = s.substr(n / 2);
		return front + back[0] + back;
	}
	for(int i=0;i<n;i++){
		if(s[i] != s[n-i-1]){
			string front = s;
			front.insert(front.begin() + i, s[n-i-1]);
			if(isPalin(front))return front;

			string back = s;
			back.insert(back.begin() + (n - i - 1) + 1, s[i]);
			if(isPalin(back))return back;

			break;
		}
	}
	return "NA";
}

int main(){
	string s;
	cin >> s;

	cout << solve(s) << endl;
	return 0;
}