diff --git a/README.md b/README.md
index 3092ce1..7fc4dee 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,3 @@
 # leetcode
 
+I am starting out by doing the Blind 75, then Grind 75
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diff --git a/medium/3 Longest Substring Without Repeating Characters/solution.py b/medium/3 Longest Substring Without Repeating Characters/solution.py
new file mode 100644
index 0000000..3741158
--- /dev/null
+++ b/medium/3 Longest Substring Without Repeating Characters/solution.py	
@@ -0,0 +1,33 @@
+class Solution:
+    def lengthOfLongestSubstring(self, s: str) -> int:
+        """
+        >>> Solution().lengthOfLongestSubstring("abcabcbb")
+        3
+        >>> Solution().lengthOfLongestSubstring("bbbbb")
+        1
+        >>> Solution().lengthOfLongestSubstring("pwwkew")
+        3
+        """
+        if s == "":
+            return 0
+
+        beginning = 0
+        end = 1
+        longest = 0
+        while end < len(s):
+            p = s[beginning:end]
+            if s[end] in s[beginning:end]:
+                if end - beginning > longest:
+                    longest = end - beginning
+                beginning += 1
+            else:
+                end += 1
+        
+        if end - beginning > longest:
+            longest = end - beginning
+        return longest
+
+
+if __name__ == "__main__":
+    import doctest
+    doctest.testmod()
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