diff --git a/sorts/sleepsort.py b/sorts/sleepsort.py
new file mode 100644
index 000000000000..267b160cf3b3
--- /dev/null
+++ b/sorts/sleepsort.py
@@ -0,0 +1,17 @@
+from time import sleep
+
+import thread
+
+items = []
+n = int(input())
+for i in range(0, n):
+    a = int(input())
+    items.append(a)
+
+
+def sleep_sort(i):
+    sleep(i)
+    print(i)
+
+
+[thread.start_new_thread(sleep_sort, (i,)) for i in items]
diff --git a/strings/longest_valid_parenthesis.py b/strings/longest_valid_parenthesis.py
new file mode 100644
index 000000000000..a99f75c433cc
--- /dev/null
+++ b/strings/longest_valid_parenthesis.py
@@ -0,0 +1,34 @@
+def longest_valid_parenthesis(s: str) -> int:
+    """
+    Returns the length of the longest valid parenthesis
+     >>> longest_valid_parenthesis('(()')
+     2
+     >>> longest_valid_parenthesis(')()())')
+     4
+     >>> longest_valid_parenthesis('(()()()()))')
+     10
+     >>> longest_valid_parenthesis(''(())))((()(()()()())
+     8
+    """
+    stack = []
+    preceeding_matched = 0
+    res = 0
+    for char in s:
+        if char == "(":
+            stack.append(preceeding_matched)
+            preceeding_matched = 0
+        else:
+            if stack:
+                preceeding_matched += 1 + stack.pop()
+            else:
+                res = max(res, preceeding_matched)
+                preceeding_matched = 0
+    res = max(res, preceeding_matched)
+    while stack:
+        res = max(res, stack.pop())
+    return res * 2
+
+
+if __name__ == "__main__":
+    s = input()
+    print(longest_valid_parenthesis(s))