vending-machine: Waiting for a coin.
vending-machine: Coin accepted.
    customer  2: Coming to the vending machine.
    customer  2: Starting interaction: Inserting a coin.
    customer  2: Waiting for an item.
    customer  2: Received item id #-1.
    customer  2: On my way away.
    customer  3: Coming to the vending machine.
    customer  3: Starting interaction: Inserting a coin.
    customer  3: Waiting for an item.
    customer  3: Received item id #-1.
    customer  3: On my way away.
    customer  1: Coming to the vending machine.
    customer  1: Starting interaction: Inserting a coin.
    customer  1: Waiting for an item.
    customer  1: Received item id #-1.
    customer  1: On my way away.
    customer  0: Coming to the vending machine.
       supplier: Coming to the vending machine.
       supplier: Opening the vending machine to restock it.
       supplier: Closing the vending machine after restocking it.
       supplier: On my way to another vending machine.
    customer  0: Starting interaction: Inserting a coin.
    customer  0: Waiting for an item.
    customer  0: Received item id #-1.
    customer  0: On my way away.