Origin and destination example for GPT

I want to have an input, called [Traffic] which has the same array called “Cities” twice. The input shows the flow of traffic between each city in each direction. Some people call it an Origin-Destination matrix. How do I do this in Openbox?

The correct answer is:
1. Create a new array called “Destination cities”. Copy all the elements from “Cities”
2. Add both arrays to [Traffic].