import java.util.*;

public class Main {
	static Scanner sc = new Scanner(System.in);
	public static void main(String[] args) {
		String s = sc.next();
		int a = 0;
		int b = 0;

		boolean F = true;
		for (int i=0; i<s.length()/2; i++) {
			if (s.charAt(i)!=s.charAt(s.length()-i-1)) {
				a = i;
				b = s.length()-i-1;
				F = false;;
				break;
			}
		}

		if (F==true) {
			StringBuilder sb = new StringBuilder(s);
			sb.insert(sb.length()/2,sb.charAt(sb.length()/2));
			System.out.println(sb);
		}
		else {
			StringBuilder sb1 = new StringBuilder(s);
			sb1.insert(a,s.charAt(b));
			StringBuilder sb2 = new StringBuilder(s);
			sb2.insert(b+1,s.charAt(a));
			if (IsPalindrome(sb1)) {System.out.println(sb1);}
			else if (IsPalindrome(sb2)) {System.out.println(sb2);}
			else {System.out.println("NA");}
		}
	}

	static boolean IsPalindrome (StringBuilder sb) {
		for (int i=0; i<sb.length()/2; i++) {
			if (sb.charAt(i)!=sb.charAt(sb.length()-i-1)) {
				return false;
			}
		}
		return true;
	}
}