Table schema:
CREATE TABLE Prescribes (patient VARCHAR, Medication VARCHAR); CREATE TABLE patient (SSN VARCHAR); CREATE TABLE Medication (Code VARCHAR, name VARCHAR)

Question: 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')