instruction: provide the number of patients with a diagnoses of personal history of other malignant neoplasm of rectum, rectosigmoid junction and anus and are still alive.
response: SELECT COUNT(DISTINCT demographic.subject_id) FROM demographic INNER JOIN diagnoses ON demographic.hadm_id = diagnoses.hadm_id WHERE demographic.expire_flag = "0" AND diagnoses.short_title = "Hx-rectal & anal malign"