from collections import deque n = int(input()) d = deque() for _ in range(n): x =input().split() m = x[0] try: v= x[1] except Exception as e: pass

match m:
    case "append":
        d.append(v)
    case "appendleft":
        d.appendleft(v)
    case "pop":
        d.pop()
    case "popleft":
        d.popleft()
    case _:
        print(-1)

#

print(*d)