Three cards of numbers from 1 to 9 are used to create a certain three-digit number. If the hundredth place is 7 and the tens place is 4, how many digits can be placed in the ones place?
1 9 1 [OP_LIST_ARANGE] [OP_LIST_SOL] 7 4 [OP_LIST_EOL] [OP_SET_DIFFERENCE] [OP_LIST_LEN]
var_a = 1
var_b = 9
var_c = 1
list_a = [i for i in range(var_a, var_b + 1, var_c)]
var_d = 7
var_e = 4
list_b= []
if "/" in str(var_e):
    var_e = eval(str(var_e))
list_b.append(var_e)
if "/" in str(var_d):
    var_d = eval(str(var_d))
list_b.append(var_d)
list_b.reverse()
list_c = list(set(list_a) - set(list_b))
var_f = len(list_c)
print(int(var_f))