what is the number of patients whose days of hospital stay is greater than 16 and item id is 51250?
CREATE TABLE prescriptions (
    subject_id text,
    hadm_id text,
    icustay_id text,
    drug_type text,
    drug text,
    formulary_drug_cd text,
    route text,
    drug_dose text
)

CREATE TABLE procedures (
    subject_id text,
    hadm_id text,
    icd9_code text,
    short_title text,
    long_title text
)

CREATE TABLE diagnoses (
    subject_id text,
    hadm_id text,
    icd9_code text,
    short_title text,
    long_title text
)

CREATE TABLE demographic (
    subject_id text,
    hadm_id text,
    name text,
    marital_status text,
    age text,
    dob text,
    gender text,
    language text,
    religion text,
    admission_type text,
    days_stay text,
    insurance text,
    ethnicity text,
    expire_flag text,
    admission_location text,
    discharge_location text,
    diagnosis text,
    dod text,
    dob_year text,
    dod_year text,
    admittime text,
    dischtime text,
    admityear text
)

CREATE TABLE lab (
    subject_id text,
    hadm_id text,
    itemid text,
    charttime text,
    flag text,
    value_unit text,
    label text,
    fluid text
)
SELECT COUNT(DISTINCT demographic.subject_id) FROM demographic INNER JOIN lab ON demographic.hadm_id = lab.hadm_id WHERE demographic.days_stay > "16" AND lab.itemid = "51250"
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: what is the number of patients whose days of hospital stay is greater than 16 and item id is 51250? ### Input: CREATE TABLE prescriptions (
    subject_id text,
    hadm_id text,
    icustay_id text,
    drug_type text,
    drug text,
    formulary_drug_cd text,
    route text,
    drug_dose text
)

CREATE TABLE procedures (
    subject_id text,
    hadm_id text,
    icd9_code text,
    short_title text,
    long_title text
)

CREATE TABLE diagnoses (
    subject_id text,
    hadm_id text,
    icd9_code text,
    short_title text,
    long_title text
)

CREATE TABLE demographic (
    subject_id text,
    hadm_id text,
    name text,
    marital_status text,
    age text,
    dob text,
    gender text,
    language text,
    religion text,
    admission_type text,
    days_stay text,
    insurance text,
    ethnicity text,
    expire_flag text,
    admission_location text,
    discharge_location text,
    diagnosis text,
    dod text,
    dob_year text,
    dod_year text,
    admittime text,
    dischtime text,
    admityear text
)

CREATE TABLE lab (
    subject_id text,
    hadm_id text,
    itemid text,
    charttime text,
    flag text,
    value_unit text,
    label text,
    fluid text
) ### Response: SELECT COUNT(DISTINCT demographic.subject_id) FROM demographic INNER JOIN lab ON demographic.hadm_id = lab.hadm_id WHERE demographic.days_stay > "16" AND lab.itemid = "51250"