Should I report the child support payment as the "setoff" amount we agreed (what I pay to my ex minus what my ex pays me) or should I report that I pay X and ex pays Y?

Both my ex and I pay child support to the other for 2 children's. I'm higher income, so for convenience we agree only one payment from me to her. How this should be reported in taxes? One payment I make, or both a payment I make and a payment that I receive?