type Cell:
    cell0
    cell1
    cell2
    cell3
    cell4
    cell5
    cell6
    
task Main(cell5 & cell6):
    complete()

task Pickup(cell & !carry) on Cell as cell:
    carry = pickup(cell)
effects:
    cell = false
    carry = true

task Dropoff(!cell & carry) on Cell as cell:
    dropoff(cell, carry)
effects:
    cell = true
    carry = false