Implement a queue with 2 stacks . Your queue should have an enqueue and a dequeue function and it should be "first in first out" (FIFO). Optimize for the time cost of m function calls on your queue. These can be any mix of enqueue and dequeue calls. Assume you already have a stack implementation and it gives O(1) time push and pop.

queue-with-stack.py

stack1 = []
stack2 = []

def enqueuue(a):
    stack1.append(a)

def dequeue():
    if len(stack2) > 0:
       return stack2.pop()
    elif len(stack2) == 0 and len(stack1) > 0:
        while(len(stack1) > 0):
            stack2.append(stack1.pop())
        return stack2.pop()
    else:
        return "Stack Underflow"

print dequeue()
enqueue(10)
enqueue(9)
enqueue(8)
print dequeue()
print dequeue()
enqueue(7)
print dequeue()
print dequeue()
print dequeue()
enqueue(6)
print dequeue()