1284 -> [0, 100, 200, 100, 200, 300, 600]
1285 -> [0, 100, 200, 100, 200, 300, 500, 999]
1286 -> [0, 100, 200, 300, 600]
...
13023 -> [0, 100, 170, 100, 200]

0 -> 100
100 -> 200
200 -> 100
100 -> 200
200 -> 300
300 -> 100

list_1284 = [0, 100, 200, 100, 200, 300, 600]

set_1284 = set(list_1284)

if len(set_1284) != len(list_1284):
   print "There exists a loop"

else:
   print "No loop exists"