import java.util.*;

public class PalDemo {

	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);
	}
	
	public static boolean isPalindrome(String input) {
		
		Queue<Character> q = new LinkedList<Character>();
		Stack<Character> s = new Stack<Character>();
		Character c;
		int mismatches = 0;
		int i;
		
		for (i = 0; i < input.length(); i++) {
			c = input.charAt(i);
			if (Character.isLetter(c)) {
				q.add(c);
				s.push(c);
			}
		}
		
		while (!q.isEmpty()) {
			if (q.remove() != s.pop())
				mismatches++;
		}
		
		return (mismatches == 0);
	}
}