On the fifth day after a casual sexual contact a 25-year-old female patient consulted a doctor about purulent discharges from the genital tracts and itch. Vaginal examination showed that vaginal part of uterine cervix was hyperemic and edematic. There was an erosive area around the external orifice of uterus. There were mucopurulent profuse discharges from the cervical canal, uterine body and appendages exhibited no changes. Bacterioscopic examination revealed bean-shaped diplococci that became red after Gram's staining. What is the most likely diagnosis?