Apply operation to the first 2 items of the output queue

    op_stack Deque (reference)
    out_stack Deque (reference)

def apply_operation(op_stack, out_stack):
    """
    Apply operation to the first 2 items of the output queue

    op_stack Deque (reference)
    out_stack Deque (reference)
    """
    out_stack.append(calc(out_stack.pop(), out_stack.pop(), op_stack.pop()))