diff --git a/abducer/kb.py b/abducer/kb.py
index 7fa4b3f..8c3f49a 100644
--- a/abducer/kb.py
+++ b/abducer/kb.py
@@ -127,7 +127,7 @@ class add_KB(ClsKB):
     
 class hwf_KB(ClsKB):
     def __init__(self, GKB_flag = False, \
-                    pseudo_label_list = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '-', '*', '/'], \
+                    pseudo_label_list = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '-', 'times', 'div'], \
                     len_list = [1, 3, 5, 7]):
         super().__init__(GKB_flag, pseudo_label_list, len_list)
         
@@ -137,7 +137,7 @@ class hwf_KB(ClsKB):
         for i in range(len(formula)):
             if i % 2 == 0 and formula[i] not in ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9']:
                 return False
-            if i % 2 != 0 and formula[i] not in ['+', '-', '*', '/']:
+            if i % 2 != 0 and formula[i] not in ['+', '-', 'times', 'div']:
                 return False
         return True
     
@@ -145,6 +145,8 @@ class hwf_KB(ClsKB):
         if not self.valid_candidate(formula):
             return np.inf
         try:
+            mapping = {'0':'0', '1':'1', '2':'2', '3':'3', '4':'4', '5':'5', '6':'6', '7':'7', '8':'8', '9':'9', '+':'+', '-':'-', 'times':'*', 'div':'/'}
+            formula = [mapping[f] for f in formula]
             return round(eval(''.join(formula)), 2)
         except ZeroDivisionError:
             return np.inf