def pop(self): if deque.size() == 0: return -1 else: return self.deque.popleft()
def back(self): if deque.size() == 0: return -1 else: return self.deque[-1]
def empty(self): if deque.size() == 0: return 1 else: return 0
def front(self): if deque.size() == 0: return -1 else: return self.deque[0]
def front(self): if deque.size() == 0: return -1 else: return self.deque[0] def back(self): if deque.size() == 0: return -1 else: return self.deque[-1] deque = Queue() N = int(sys.stdin.readline()) for i in range(N): str = sys.stdin.readline().rstrip().split(' ') if str[0] == 'push': deque.push(int(str[1])) elif str[0] == 'front': print(deque.front()) elif str[0] == 'size': print(deque.size()) elif str[0] == 'empty': print(deque.empty()) elif str[0] == 'back': print(deque.back()) elif str[0] == 'pop': print(deque.pop())