diff --git "a/leetcode3/\353\202\250\355\232\250\354\240\225/1539. Kth Missing Positive Number.py" "b/leetcode3/\353\202\250\355\232\250\354\240\225/1539. Kth Missing Positive Number.py"
new file mode 100644
index 00000000..dba6bd71
--- /dev/null
+++ "b/leetcode3/\353\202\250\355\232\250\354\240\225/1539. Kth Missing Positive Number.py"	
@@ -0,0 +1,10 @@
+class Solution:
+    def findKthPositive(self, arr: List[int], k: int) -> int:
+        miss_num = 0
+        cnt = 0
+        while True:
+            miss_num += 1
+            if miss_num not in arr:
+                cnt += 1
+            if k == cnt:
+                return miss_num
\ No newline at end of file
diff --git "a/leetcode3/\353\202\250\355\232\250\354\240\225/611. Valid Triangle Number.py" "b/leetcode3/\353\202\250\355\232\250\354\240\225/611. Valid Triangle Number.py"
new file mode 100644
index 00000000..78f27e3b
--- /dev/null
+++ "b/leetcode3/\353\202\250\355\232\250\354\240\225/611. Valid Triangle Number.py"	
@@ -0,0 +1,20 @@
+# 풀이 실패
+class Solution:
+    def triangleNumber(self, nums: List[int]) -> int:
+        nums.sort()
+        cnt = 0
+        N = len(nums)
+        
+        for k in range(N-1, 1, -1):
+            left = 0
+            right = k - 1
+
+            # 투 포인터
+            while left < right:
+                if nums[left] + nums[right] > nums[k]:
+                    cnt += right - left
+                    right -= 1
+                else:
+                    left += 1
+
+        return cnt