import java.util.*;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int i, n = sc.nextInt(), t;
        String ac = null;
        boolean[] errors = new boolean[10001];
        Deque<Integer> dq = new ArrayDeque();
        for (i = 1; i <= n; i++) {
            ac = sc.next();
            errors[i] = false;
            if ("LIN".equals(ac)) {
                t = sc.nextInt();
                dq.addFirst(t);
            } else if ("RIN".equals(ac)) {
                t = sc.nextInt();
                dq.addLast(t);
            } else if ("LOUT".equals(ac)) {
                if (dq.size() > 0) dq.removeFirst();
                else {
                    errors[i] = true;
                }
            } else if ("ROUT".equals(ac)) {
                if (dq.size() > 0) dq.removeLast();
                else {
                    errors[i] = true;
                }
            }
        }
        while (dq.size() > 0) {
            System.out.print(dq.getFirst() + " ");
            dq.pop();
        }
        System.out.println();
        for (i = 1; i <= n; i++) {
            if (errors[i] == true) {
                System.out.println(i+" ERROR");
            }
        }
        sc.close();
    }
}

/**************************************************************
	Problem: 1789
	User: admin
	Language: Java
	Result: Accepted
	Time:987 ms
	Memory:42416 kb
****************************************************************/