Cops are looking for the perv who sexually assaulted a woman on the Upper East Side, police said Wednesday.

The 21-year-old woman was standing on the corner of East 77th Street and York Avenue around 11:35 p.m. on Jan. 20 when the man approached her and reached into her pants and grabbed her breasts before running away, cops said.

The creep was last seen wearing a blue puffer jacket, blue hoodie, and black sweatpants. Anyone with information is asked to call the NYPD’s Crime Stoppers Hotline at 1-800-577-TIPS (8477).