How do we review a federal district court's sentencing decision for procedural error?

We review a district court's sentencing decision for procedural and substantive reasonableness "under a deferential abuse-of-discretion standard." United States v. Cavera, 550 F.3d 180, 189 (2d Cir. 2008) (internal quotation marks omitted). A sentencing court commits procedural error if, among other things, it "treats the Guidelines as mandatory," "does not consider the [18 U.S.C.] 3553(a) factors," or "fails adequately to explain its chosen sentence." Id. at 190. A sentence is substantively unreasonable "only in exceptional cases where the trial court's decision cannot be located within the range of permissible decisions." Id. at 189 (internal quotation marks omitted).