class Queue:
def __init__(self):
self.length = 0
self.s1 = Stack()
self.s2 = Stack()
def Insert(self, elem):
self.s1.Push(elem)
self.length += 1
def Remove(self):
if self.s2.Is_Empty():
#switch the entire stack over s2
while not self.s1.Is_Empty():
node = self.s1.Pop()
self.s2.Push(node)
elem = self.s2.Pop()
self.length -= 1
return str(elem)
def Is_Empty(self):
return self.length == 0
