diff --git a/artificial_detection/models/smr/sais.py b/artificial_detection/models/smr/sais.py
index 252690b..e2d3027 100644
--- a/artificial_detection/models/smr/sais.py
+++ b/artificial_detection/models/smr/sais.py
@@ -1,3 +1,4 @@
+import numpy as np
 def construct_suffix_array(string):
     ta = construct_type_array(string)
     mapping = construct_alphabet_mapping(string)
@@ -167,14 +168,10 @@ def construct_buckets(encoded_string, mapping):
 
 
 def get_bucket_heads(buckets):
-    heads = [0]
-    for bucket_size in buckets[:-1]:
-        heads.append(heads[-1] + bucket_size)
+    heads = [0] + np.cumsum(buckets[:-1]).tolist()
     return heads
 
 
 def get_bucket_tails(buckets):
-    tails = [0]
-    for bucket_size in buckets[1:]:
-        tails.append(tails[-1] + bucket_size)
+    tails = [0] + np.cumsum(buckets[1:]).tolist()
     return tails