import java.util.*;

public class QueueClient {


  public static void main(String []args) {
    LinkedListBasedQueue<String> q;
    q = new LinkedListBasedQueue<String>();
    Scanner scan = new Scanner (System.in);
    
    while (scan.hasNext()) {
      String inputString = scan.next();
      if (inputString.equals("d")) 
        System.out.println(q.deQ());
      else
        q.enQ(inputString);
    }
  }
}