I have a four columns Input like
address 1 address 2 address 3 address 4
Null L1 L2 L3
L1 L2 L3 Null
L1 Null L2 L3L1 L2 Null L3Output Required
L1 L2 L3 NullL1 L2 L3 Null
This will solve it for you. Workflow is attached!