diff --git a/abducer/kb.py b/abducer/kb.py
index 5d25a46..12772e5 100644
--- a/abducer/kb.py
+++ b/abducer/kb.py
@@ -45,9 +45,9 @@ class KBBase(ABC):
         pass
 
 class add_KB(KBBase):
-    def __init__(self, pseudo_label_list, kb_max_len = -1):
+    def __init__(self, kb_max_len = -1):
         super().__init__()
-        self.pseudo_label_list = pseudo_label_list
+        self.pseudo_label_list = list(range(10))
         self.base = {}
         self.kb_max_len = kb_max_len
         if(self.kb_max_len > 0):
@@ -92,9 +92,9 @@ class add_KB(KBBase):
         return sum(self._dict_len(v) for v in self.base.values())
     
 class hwf_KB(KBBase):
-    def __init__(self, pseudo_label_list, kb_max_len = -1):
+    def __init__(self, kb_max_len = -1):
         super().__init__()
-        self.pseudo_label_list = pseudo_label_list
+        self.pseudo_label_list = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '-', '*', '/']
         self.base = {}
         self.kb_max_len = kb_max_len
         if(self.kb_max_len > 0):
@@ -157,13 +157,13 @@ class hwf_KB(KBBase):
     
     def valid_formula(self, formula):
         symbol_idx_list = []
-        first_minus_flag = 0
         for idx, c in enumerate(formula):
             if(idx == 0 and c == '-'):
-                first_minus_flag = 1
+                if(len(formula) == 1 or formula[1] in ['+', '-', '*', '/']):
+                    return False
                 continue
             if(c in ['+', '-', '*', '/']):
-                if(idx - 1 in symbol_idx_list or (idx == 1 and first_minus_flag == 1)):
+                if(idx - 1 in symbol_idx_list):
                     return False
                 symbol_idx_list.append(idx)
         if(0 in symbol_idx_list or len(formula) - 1 in symbol_idx_list):
@@ -289,8 +289,7 @@ class reg_KB(KBBase):
 
 if __name__ == "__main__":
     # With ground KB
-    pseudo_label_list = list(range(10))
-    kb = add_KB(pseudo_label_list, kb_max_len = 5)
+    kb = add_KB(kb_max_len = 5)
     print('len(kb):', len(kb))
     res = kb.get_candidates(0)
     print(res)
@@ -303,8 +302,7 @@ if __name__ == "__main__":
     print()
     
     # Without ground KB
-    pseudo_label_list = list(range(10))
-    kb = add_KB(pseudo_label_list)
+    kb = add_KB()
     print('len(kb):', len(kb))
     res = kb.get_candidates(0)
     print(res)
@@ -316,8 +314,7 @@ if __name__ == "__main__":
     print(res)
     print()
     
-    pseudo_label_list = ['1', '2', '3', '4', '5', '6', '7', '8', '9', '0', '+', '-', '*', '/']
-    kb = hwf_KB(pseudo_label_list, kb_max_len = 5)
+    kb = hwf_KB(kb_max_len = 5)
     print('len(kb):', len(kb))
     res = kb.get_candidates(1, length = 3)
     print(res)