Queue Made of Two Stacks

Build a class StackQueue that behaves like a first-in first-out queue of ints but is implemented with two stack<int> members only (no queue, deque or vector).

Implement these public methods:
1. void enqueue(int x) — adds x to the back of the queue
2. int dequeue() — removes and returns the element at the front of the queue; if the queue is empty, return -1
3. int size() const — returns the total number of elements as an int

Example: after enqueue(1) and enqueue(2) the test calls dequeue() three times and prints each result on its own line (see Expected Output).

Do NOT write a main function.