Find the number of cases in which A or B is at the forefront when three of the four students are selected from A, B, C, and D and placed in a line.
[OP_LIST_SOL] A B [OP_LIST_EOL] [OP_LIST_LEN] 4 1 [OP_SUB] 3 1 [OP_SUB] [OP_COMB] [OP_MUL] 3 1 [OP_SUB] 3 1 [OP_SUB] [OP_PERM] [OP_MUL]
var_a = 'A'
var_b = 'B'
list_a= []
if "/" in str(var_b):
    var_b = eval(str(var_b))
list_a.append(var_b)
if "/" in str(var_a):
    var_a = eval(str(var_a))
list_a.append(var_a)
list_a.reverse()
var_c = len(list_a)
var_d = 4
var_e = 1
var_f = var_d - var_e
var_g = 3
var_h = 1
var_i = var_g - var_h
var_j = 1
var_f = int(var_f)
var_i = int(var_i)
for i, elem in enumerate(range(var_i)):
    var_j = var_j * (var_f-i)
for i, elem in enumerate(range(var_i)):
    var_j = var_j / (i+1)
var_k = var_c * var_j
var_l = 3
var_m = 1
var_n = var_l - var_m
var_o = 3
var_p = 1
var_q = var_o - var_p
var_r = 1
var_n = int(var_n)
var_q = int(var_q)
for i, elem in enumerate(range(var_q)):
    var_r = var_r * (var_n-i)
var_s = var_k * var_r
print(int(var_s))