package no238;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String s = sc.next();
		ArrayList<Character> ans = solve(s);
		if (ans == null) {
			System.out.println("NA");
		}else{
			StringBuilder sb = new StringBuilder();
			for(char c:ans) {
				sb.append(c);
			}
			System.out.println(sb.toString());
		}
	}

	public static ArrayList<Character> solve(String s) {
		int n = s.length();
		ArrayList<Character> a = new ArrayList<>();
		for(int i=0;i<n;i++) {
			a.add(s.charAt(i));
		}
		if (isKaibun(a)) {
			a.add(n/2, a.get(n/2));
			return a;
		}
		ArrayList<Character> b = new ArrayList<>(a);
		Collections.reverse(b);
		for(int i=0;i<n;i++) {
			char c1 = a.get(i);
			char c2 = b.get(i);
			if (c1 != c2) {
				a.add(i,c2);
				if (isKaibun(a)) {
					return a;
				}
				b.add(i,c1);
				if (isKaibun(b)) {
					return b;
				}
				return null;
			}
		}
		return null; //unreachable
	}

	public static boolean isKaibun(ArrayList<Character> a) {
		int n = a.size();
		for(int i=0;i<n/2;i++) {
			if (a.get(i) != a.get(n-1-i)) {
				return false;
			}
		}
		return true;
	}

}