Five animals are on the way: Rat, Cow, Tiger, Rabbit, Dragon and Snake. The mouse with the best eye sight should come first, and the snake with the longest tail should come last. Find the number of all cases in which five animals form a line.
[OP_LIST_SOL] Rat Cow Tiger Rabbit Dragon Snake [OP_LIST_EOL] [OP_LIST_SOL] Rat [OP_LIST_EOL] [OP_SET_DIFFERENCE] [OP_LIST_SOL] Snake [OP_LIST_EOL] [OP_SET_DIFFERENCE] [OP_LIST_LEN] [OP_LIST_LEN] [OP_PERM]
var_a = 'Rat'
var_b = 'Cow'
var_c = 'Tiger'
var_d = 'Rabbit'
var_e = 'Dragon'
var_f = 'Snake'
list_a= []
if "/" in str(var_f):
    var_f = eval(str(var_f))
list_a.append(var_f)
if "/" in str(var_e):
    var_e = eval(str(var_e))
list_a.append(var_e)
if "/" in str(var_d):
    var_d = eval(str(var_d))
list_a.append(var_d)
if "/" in str(var_c):
    var_c = eval(str(var_c))
list_a.append(var_c)
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_g = 'Rat'
list_b= []
if "/" in str(var_g):
    var_g = eval(str(var_g))
list_b.append(var_g)
list_b.reverse()
list_c = list(set(list_a) - set(list_b))
var_h = 'Snake'
list_d= []
if "/" in str(var_h):
    var_h = eval(str(var_h))
list_d.append(var_h)
list_d.reverse()
list_e = list(set(list_c) - set(list_d))
var_i = len(list_e)
var_j = len(list_e)
var_k = 1
var_i = int(var_i)
var_j = int(var_j)
for i, elem in enumerate(range(var_j)):
    var_k = var_k * (var_i-i)
print(int(var_k))