A 14-year-old girl complains of profuse bloody discharges from genital tracts during 10 days after suppresion of menses for 1,5 month. Similiar bleedings recur since 12 years on the background of disordered menstrual cycle. On rectal examination: no pathology of the internal genitalia. In blood: Hb - 70 g/l, RBC-2,3 × 1012/l, Ht - 20. What is the most probable diagnosis?