diff --git a/medium/string_compression_iii.py b/medium/string_compression_iii.py
new file mode 100644
index 0000000..72d4a28
--- /dev/null
+++ b/medium/string_compression_iii.py
@@ -0,0 +1,29 @@
+# https://leetcode.com/problems/string-compression-iii
+
+class Solution:
+    def compressedString(self, word: str) -> str:
+        last_char = None
+        l = 0
+        result = []
+        def to_string(ch, cnt, result):
+            if cnt <= 9:
+                result.append(str(cnt))
+                result.append(ch)
+            else:
+                cnt -= 9
+                result.append('9')
+                result.append(ch)
+                to_string(ch, cnt, result)
+        for ch in word:
+            if last_char == None:
+                last_char = ch
+                l = 1
+                continue
+            if last_char != ch:
+                to_string(last_char, l, result)
+                l = 1
+                last_char = ch
+            else:
+                l += 1
+        to_string(last_char, l, result)
+        return ''.join(result)