Implement the following operations of a queue using stacks.
You must use only standard operations of a stack -- which means only
push to top,
peek/pop from top,
is empty operations are valid.
Depending on your language, stack may not be supported natively. You may simulate a stack by using a list or deque (double-ended queue), as long as you use only standard operations of a stack.
You may assume that all operations are valid (for example, no pop or peek operations will be called on an empty queue).