Is my N-drome (variation of palindrome) checking program efficient?

• An N-Drome is a string that is the same forwards and backwards when split into n-character units.

• For example, a string would be a 1-drome if and only if it were a standard palindrome.

• An example of a 2-drome would be abcdab since its 2-character units are ab, cd, and ab, and its first and last 2-character units are identical.

package ndrome;

import java.util.Scanner;

public class NDrome {
    public static void main(String[] args) {
        System.out.print("enter a string: ");
        Scanner in = new Scanner(System.in);
        String original = in.nextLine();
        System.out.print("enter the n value: ");
        int n = in.nextInt();
        if(n-1>=original.length()){
            System.out.println("Error:N value is greater than string length! exiting...");
            System.exit(0);
        }
        int y = 2;
        here: for (int i = 0, j = original.length() - 1;;) {
            int x = n - 1;
            String a = "", b = "";
            while (x >= 0) {
                if (i >= original.length()) {
                    break here;
                } else {
                    a = a + original.charAt(i);
                    i++;
                    b = b + original.charAt(j - x);
                    x--;
                }
            }
            j=j-n;
            if (a.equals(b)) {
                y = 1;
            } else {
                y = 0;
                break;
            }
        }
        if (y == 1) {
            System.out.print("this is a " + n + "-drome");
        } else if (y == 0) {
            System.out.print("this is not a " + n + "-drome");
        }
    }
}