In the bookstore, all but 4 of the 40 books were sold out. There were 4 customers in total, and they all bought the same number of books. How many books did a customer buy?
40 4 [OP_SUB] 4 [OP_DIV]
var_a = 40
var_b = 4
var_c = var_a - var_b
var_d = 4
var_e = var_c / var_d
print(int(var_e))