2 days ago a 12-year-old patient prsented with body temperature rise up to 38,0°C, on the second day he developed a bilateral edema in the parotid region. The skin over the edema was tense, of normal color. Palpation revealed soft, enlarged, painful parotid salivary glands. Salivation from the parotid ducts was abnormal, the duct orifices were hyperaemic. Palpation caused pain in the angle of mandible, at the top of mastoid bone, in front of the antilobium. What is the most likely diagnosis?