Software: How to determine coordinator's 64-bit address?

My end device powers up and associates to the coordinator just fine. Now I would like to send some data to the coordinator. What is the best way to determine the 64-bit address of the coordinator?

Do I have to perform a “ND” (Node Discover)?
The ND command does not return any information that positively identifies a node as the coordinator that I have associated to.

How is this done?

Note: Hard coding the 64 bit address in the endpoint’s Flash is not an option.

Dear cesium,
If you change the default value of the MY register on the Coordinator from 0 to FFFE, then when coordination takes place, the DL and DH registers on the End Device will contain the address of the coordinator.