diff --git "a/leetcode3/\354\227\274\355\230\234\354\240\225/1539. Kth Missing Positive Number.java" "b/leetcode3/\354\227\274\355\230\234\354\240\225/1539. Kth Missing Positive Number.java"
new file mode 100644
index 00000000..c4276f7b
--- /dev/null
+++ "b/leetcode3/\354\227\274\355\230\234\354\240\225/1539. Kth Missing Positive Number.java"	
@@ -0,0 +1,21 @@
+// O(n)...
+
+class Solution {
+    public int findKthPositive(int[] arr, int k) {
+        Set<Integer> set = new HashSet<>();
+        for (int a : arr) set.add(a);
+        
+        int i = 1;
+        int cnt = 0;
+        int result = 0;
+        while(true) {
+            if (!set.contains(i)) cnt++;
+            if (cnt == k) {
+                result = i;
+                break;
+            }
+            i++;
+        }
+        return result;
+    }
+}