CREATE TABLE Prescribes (patient VARCHAR(255), Medication VARCHAR(255)); CREATE TABLE patient (SSN VARCHAR(255)); CREATE TABLE Medication (Code VARCHAR(255), name VARCHAR(255))
Find the number of patients who are not using the medication of Procrastin-X.
    
SQL: SELECT COUNT(*) FROM patient WHERE NOT SSN IN (SELECT T1.patient FROM Prescribes AS T1 JOIN Medication AS T2 ON T1.Medication = T2.Code WHERE T2.name = 'Procrastin-X')