class Stack:

    # Adds value to the end of the Queue.
    # Complexity: O(1)
    def push(value):
        pass

    # Returns value from the front of the Queue and removes it.
    # Complexity: O(1)
    def pop():
        pass

    # Returns value from the front of the Queue without removing it.
    # Complexity: O(1)
    def peek():
        pass

    # Returns the number of elements in the Queue.
    # Complexity: O(1)
    def size():
        pass
