import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.Iterator;


public class Main_yukicoder238_1 {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        Printer pr = new Printer(System.out);

        char[] s = sc.next().toCharArray();
        int n = s.length;

        int offset;
        for (offset = 0; offset < n; offset++) {
    		if (s[offset] != s[n - 1 - offset]) {
    			break;
    		}
        }

        if (offset == n) {
        	StringBuilder ret = new StringBuilder();
        	int len = (n + 1) / 2;
        	ret.append(s, 0, len);
        	ret.append(s[len - 1]);
        	ret.append(s, len, n - len);
        	
        	pr.println(ret);
        } else {
        	StringBuilder ret = new StringBuilder();
        	ret.append(s);
        	ret.insert(offset, s[n - 1 - offset]);

        	boolean res = true;
            for (int i = 0; i < ret.length(); i++) {
            	if (ret.charAt(i) != ret.charAt(ret.length() - 1 - i)) {
            		res = false;
            		break;
            	}
            }
            
            if (res) {
            	pr.println(ret);
            } else {
            	ret = new StringBuilder();
            	ret.append(s);
            	ret.insert(n - offset, s[offset]);

            	res = true;
                for (int i = 0; i < ret.length(); i++) {
                	if (ret.charAt(i) != ret.charAt(ret.length() - 1 - i)) {
                		res = false;
                		break;
                	}
                }
            }

            if (res) {
            	pr.println(ret);
            } else {
            	pr.println("NA");
            }
        }

        pr.close();
        sc.close();
    }

	@SuppressWarnings("unused")
	private static class Scanner {
		BufferedReader br;
		Iterator<String> it;
		
		Scanner (InputStream in) {
			br = new BufferedReader(new InputStreamReader(in));
		}
		
		String next() throws RuntimeException  {
			try {
				if (it == null || !it.hasNext()) {
					it = Arrays.asList(br.readLine().split(" ")).iterator();
				}
				return it.next();
			} catch (IOException e) {
				throw new IllegalStateException();
			}
		}
		
		int nextInt() throws RuntimeException {
			return Integer.parseInt(next());
		}

		long nextLong() throws RuntimeException {
			return Long.parseLong(next());
		}

		float nextFloat() throws RuntimeException {
			return Float.parseFloat(next());
		}

		double nextDouble() throws RuntimeException {
			return Double.parseDouble(next());
		}

		void close() {
			try {
				br.close();
			} catch (IOException e) {
//				throw new IllegalStateException();
			}
		}
	}

	private static class Printer extends PrintWriter {
		Printer(PrintStream out) {
			super(out);
		}
	}
}