You use only the Federal refund. Do NOT include any state refund. Here's where to find the refund amount on your Federal return:
If you filed a Form 1040, the Refund Amount is shown on Line 76a.
If you filed a Form 1040A, the Refund Amount is shown on Line 48a.
If you filed a Form 1040EZ, the Refund Amount is shown on Line 13a.