A patient complains of fever up to 38°C, headache, pain in the joints anf muscles, vesicles in the oral cavity, mainly in the frontal part. Eating is sharply painful. For the last several years the disease recurred during wet anf windy weather. The patient often suffers from cases of URTI. Objectively: on the buccal, lingual, labial mucosa there are confluent erosions against the erythematous background, covered in graywhite coating. There are bloody scabs on the red border and in the angles of the mouth. Make the diagnosis: