Toy Tractors

Contractors A, B, and C faced a shortage of tractors on a construction project, so they lent one another tractors as needed. First, A lent B and C as many tractors as each already had. A few months later, B lent A and C as many tractors as each already had. Still later, C lent A and B as many tractors as each already had. By then each contractor had 24 tractors. How many tractors did A have originally?