diff --git a/Unit 3/othello_submission.py b/Unit 3/othello_submission.py
index 8a68d20..49e6621 100644
--- a/Unit 3/othello_submission.py	
+++ b/Unit 3/othello_submission.py	
@@ -188,7 +188,7 @@ INSULTS = [
 
 class Strategy:
    def __init__(self):
-      #self.logging = True
+      self.logging = True
       self.white = "o"
       self.black = "x"
       self.directions = [[-1, -1], [-1, 0], [-1, 1], [0, -1], [0, 1], [1, -1], [1, 0], [1, 1]]
@@ -254,10 +254,10 @@ class Strategy:
 
       if search_depth % 2 == 0:
          v = -9999999999
-         result = 0
+         result = -123456789
          for move, flipped in self.find_moves(board, color).items():
             max_val, max_state = self.alphabeta(self.make_move(board, color, move, flipped), self.opposite_color[color], search_depth - 1, alpha, beta, move)
-            if v < max_val:
+            if v < max_val or result == -123456789:
                v = max_val
                result = move
             if v > beta:
@@ -266,10 +266,10 @@ class Strategy:
          return v, result
       else:
          v = 9999999999
-         result = 0
+         result = -123456789
          for move, flipped in self.find_moves(board, color).items():
             min_val, min_state = self.alphabeta(self.make_move(board, color, move, flipped), self.opposite_color[color], search_depth - 1, alpha, beta, move)
-            if v > min_val:
+            if v > min_val or result == -123456789:
                v = min_val
                result = move
             if v < alpha:
diff --git a/Unit 4/Lab_A_self_check.py b/Unit 4/Lab_A_self_check.py
new file mode 100644
index 0000000..056fc17
--- /dev/null
+++ b/Unit 4/Lab_A_self_check.py	
@@ -0,0 +1,93 @@
+# Nicole Kim, 2/9/2019, edited on 2/1/2021
+import re
+
+def num_30(str):
+   # Current test checks if the string is '0' 
+   pattern = "^10[01]$|^0$"   #notice that python does not want / /
+   match = re.match(pattern, str)
+   print ("string is either 0, 100, or 101: ", match != None)
+
+def num_31(str):
+   # Current test checks if the string is '0' 
+   pattern = "^[01]*$"
+   print ("string is a binary string:", re.match(pattern, str) != None)
+
+# Pre-condition: input is a binary string, so you do not need to check if it's a binary or not.
+def num_32(str):
+   pattern = '^.*0$'
+   print ("string is an even binary number:", re.match(pattern, str) != None)
+
+def num_33(str):
+   # Current test searches words with 'a' 
+   pattern = "\w*[aeiou]\w*[aeiou]\w*"
+   # Notice that python does not support /i in the pattern. 
+   # Use re.I for case insensitive when you match(exact same) or search(has one or more)
+   print ("there's a word at least two vowels:", re.search(pattern, str, re.I) != None)
+
+def num_34(str):
+   pattern = "^1[10]*0$"
+   print ("even binary integer string:", re.match(pattern, str) != None)
+
+def num_35(str):
+   pattern = "^[10]*110[10]*$"
+   print ("binary string including 110:", re.match(pattern, str) != None)
+
+def num_36(str):
+   pattern = ".{2,4}$"
+   print ("length at least two, but at most four:", re.match(pattern, str, re.DOTALL) != None)
+
+def num_37(str):
+   pattern = "^\d{3}[- ]*\d{2}[- ]*\d{4}$"
+   print ("valid social security number:", re.match(pattern, str) != None)
+
+def num_38(str):
+   # When you read multiline input such as "I\nAM\nSAM."
+   # str = str.replace('\\n', '\n') # If you need this...
+   pattern = "^\w*d\w*"
+   
+   # When you want to use /im options:
+   d_search = re.search(pattern, str, re.I | re.MULTILINE)
+   print ("first word with d on a line:", d_search != None)
+
+def num_39(str):
+   pattern = "^1[10]*1$|^0[10]*0$"
+   print ("There's same number of 01 substrings as 10 substrings: ", re.match(pattern, str) != None)
+
+while(True):
+   input_num = input("Choose the exercise # (30 - 39 or -1 to terminate):")
+   if input_num == '-1': exit("Good bye")
+   input_str = input("Input string: ")
+   try:
+      eval("num_" + input_num)(input_str)
+   except:
+      pass
+   print()
+   
+''' Sample Output
+Choose the exercise # (30 - 39 or -1 to terminate):30
+Input string: 100
+string is either 0, 100, or 101:  True
+
+Choose the exercise # (30 - 39 or -1 to terminate):30
+Input string: 1000
+string is either 0, 100, or 101:  False
+
+Choose the exercise # (30 - 39 or -1 to terminate):39
+Input string: 101
+There's same number of 01 substrings as 10 substrings:  True
+
+Choose the exercise # (30 - 39 or -1 to terminate):39
+Input string: 100
+There's same number of 01 substrings as 10 substrings:  False
+
+Choose the exercise # (30 - 39 or -1 to terminate):39
+Input string: 0
+There's same number of 01 substrings as 10 substrings:  True
+
+Choose the exercise # (31 - 40 or -1 to terminate):-1
+Good bye
+
+ ----jGRASP wedge2: exit code for process is 1.
+ ----jGRASP: operation complete.
+
+'''
\ No newline at end of file
diff --git a/Unit 4/Umaretiya_r_U4_A.txt b/Unit 4/Umaretiya_r_U4_A.txt
new file mode 100644
index 0000000..8c7e5a6
--- /dev/null
+++ b/Unit 4/Umaretiya_r_U4_A.txt	
@@ -0,0 +1 @@
+A
\ No newline at end of file