import java.util.*;

public class PalDemo2 {

	public static void main(String[] args) {
		Scanner stdin = new Scanner(System.in);
		String line;
		
		do {
			System.out.print("Your expression (or return to end): ");
			line = stdin.nextLine();
			if (line.length() == 0)
				break;
			if (isPalindrome(line))
				System.out.println("That is a palindrome");
			else
				System.out.println("That is not a palindrome."); 
		} while (true);
	}
	
	// Returns true if the given string reads the same
	// forwards as backwards.
	// Trivially true for empty or 1-letter strings.
	public static boolean isPalindrome(String s) {
	    if (s.length() < 2) {
	        return true;   // base case
	    } else {
	        char first = s.charAt(0);
	        char last  = s.charAt(s.length() - 1);
	        if (first != last) {
	            return false;
	        }              // recursive case
	        String middle = s.substring(1, s.length() - 1);
	        return isPalindrome(middle);
	    }
	}

}