diff --git a/hard/k_th_smallest_in_lexicographical_order.py b/hard/k_th_smallest_in_lexicographical_order.py
new file mode 100644
index 0000000..1f73dcc
--- /dev/null
+++ b/hard/k_th_smallest_in_lexicographical_order.py
@@ -0,0 +1,24 @@
+# https://leetcode.com/problems/k-th-smallest-in-lexicographical-order
+
+class Solution:
+    def findKthNumber(self, n: int, k: int) -> int:
+        def max_step(curr: int) -> int:
+            step = 0
+            first, last = curr, curr
+            while first <= n:
+                step += min(n, last) - first + 1
+                first *= 10
+                last = last * 10 + 9
+            return step
+        curr = 1
+        k -= 1
+        while k > 0:
+            step = max_step(curr)
+            if step <= k:
+                k -= step
+                curr += 1
+            else:
+                k -= 1
+                curr *= 10
+        return curr
+