import java.util.*;

public class Main {
	static Scanner sc = new Scanner(System.in);
	public static void main(String[] args) {
		StringBuilder sb = new StringBuilder(sc.next());
		StringBuilder ans = new StringBuilder("NA");
		
		if (sb.length()%2==0) {
			String s = sb.toString();
			String str = sb.insert(sb.length()/2,"a").reverse().toString();
			sb.setLength(0);
			sb.append(s);
			
			for (int i=0; i<=sb.length(); i++) {
				sb.insert(i,str.charAt(i));
				int count = 0;
				for (int j=0; j<sb.length()/2; j++) {
					if (sb.charAt(j)==sb.charAt(sb.length()-j-1)) {
						count++;
						if (count == sb.length()/2) {ans=sb; break;}
					}
				}
				sb.delete(i,i+1);
			}
			
		}
		else if (sb.length()%2!=0) {
			String s = sb.toString();
			String str = sb.insert(sb.length()/2,sb.charAt(sb.length()/2)).reverse().toString();
			sb.setLength(0);
			sb.append(s);
			
			for (int i=0; i<=sb.length(); i++) {			
				sb.insert(i,str.charAt(i));
				int count = 0;
				for (int j=0; j<sb.length()/2; j++) {
					if (sb.charAt(j)==sb.charAt(sb.length()-j-1)) {
						count++;
						if (count == sb.length()/2) {ans=sb; break;}
					}
				}
				sb.delete(i,i+1);
			}
			
		}
		
		System.out.println(ans);
	}
}