A 48-year-old patient complains of subfebrile temperature and a growing ulcer on the gingival mucosa around the molars; teeth mobility in the affected area, cough. Objectively: gingival mucosa in the region of the lower left molars has two superficial extremely painful ulcers with undermined edges. The ulcers floor is yellowish, granular, covered with yellowish and isolated pink granulations. The ulcers are surrounded by the tubercles. Dental cervices are exposed, there is a pathological tooth mobility. Regional lymph nodes are enlarged and make dense matted together groups. What is the most likely diagnosis?