diff --git a/JYPARK/21to30/27.py b/JYPARK/21to30/27.py
new file mode 100644
index 0000000..02a7cf0
--- /dev/null
+++ b/JYPARK/21to30/27.py
@@ -0,0 +1,56 @@
+class Node:
+    def __init__(self, key):
+        self.left = None
+        self.right = None
+        self.val = key
+    
+class BST:
+    def __init__(self):
+        self.root = None
+    def insert(self, key):
+        #루트 노드가 없는 경우 새로운 노드를 루트 노드로 추가
+        if not self.root:
+            self.root = Node(key)
+        else:
+            curr = self.root
+            while True:
+                if key < curr.val:
+                    if curr.left:
+                        curr = curr.left
+                    else:
+                        curr.left = Node(key)
+                        break
+                else:
+                    if curr.right:
+                        curr = curr.right
+                    else:
+                        curr.right = Node(key)
+                        break
+    def search(self, key):
+        curr = self.root     
+        while curr and curr.val != key:
+            if key < curr.val:
+                curr = curr.left
+            else:
+                curr = curr.right
+        return curr
+
+
+def solution(lst, search_lst):
+    answer = []
+    bst = BST()
+    for node in lst:
+        bst.insert(node)
+
+    for key in search_lst:
+        result = bst.search(key)  #Node객체가 반환된다
+        if result != None and result.val == key:
+            answer.append(True)
+        else:
+            answer.append(False)
+    return answer
+
+lst = [5, 3, 8, 4, 2, 1, 7, 10]
+search_lst = [1, 2, 5, 6]
+#solution(lst, search_lst)
+print(solution(lst, search_lst))
\ No newline at end of file