[calc] double arrow

What is the easiest way to draw a double -in single -out arrow?
example drawn below

|  a |
    :                        ____
    :---------------------> |  c |
    :                       |____|
 __ :_
|  b  |

Can this be of help? :

[Glue points and Connectors](https://wiki.documentfoundation.org/Videos/Drawing_basic_shapes_in_Draw#Glue_points_and_Connectors)

Maybe you can add a connector between a and b, and a arrowed line from the connector to c.

Have a look in Gallery. I have folders FlowChart and BPMN that contain something along those lines, BPMN in particular has some gateway-or-merge arrows

After some tests, I decided to use simple shapes due their ease and flexibility; none of the above-mentioned solutions fit well, mainly because not much customisable