import time


class DelayQueue:
    def __init__(self, recovery: int, burst=0):
        self.recovery = recovery
        self.burst = burst
        self.items = []
        self.next_packet = 0

    def enqueue(self, item):
        self.items.insert(0, item)

    def dequeue(self):
        if self.items:
            t = time.time()
            time_with_burst = t - (self.burst * self.recovery)
            if self.next_packet < time_with_burst:
                self.next_packet = time_with_burst

            if t >= self.next_packet:
                self.next_packet += self.recovery
                return self.items.pop()
        else:
            return None

    def __len__(self):
        return len(self.items)

    def clear(self):
        self.items = []

    def is_empty(self):
        return len(self.items) == 0