import java.util.ArrayDeque;
import java.util.Scanner;

public class L08_BrowserHistoryExtend {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        ArrayDeque<String> stack = new ArrayDeque<>();
        ArrayDeque<String> queue = new ArrayDeque<>();


        String input;
        while (!"Home".equals(input = scanner.nextLine())) {
            String currentInput = "";
            if ("back".equals(input)) {
                if (stack.size() <= 1) {
                    System.out.println("no previous URLs");
                    continue;
                } else {
                    queue.offer(stack.pop());
                    currentInput = stack.peek();
                }
            } else if ("forward".equals(input)) {
                if (queue.size() < 1) {
                    System.out.println("no next URLs");
                    continue;
                }else {

                    currentInput = queue.peek();
                    queue.poll();
                }
            } else {
                currentInput = input;
                stack.push(input);

            }
            System.out.println(currentInput);
        }
    }
}