diff --git a/wkdghdwns199/README.md b/wkdghdwns199/README.md
index 47a02ed..997e9b9 100644
--- a/wkdghdwns199/README.md
+++ b/wkdghdwns199/README.md
@@ -9,3 +9,5 @@
 | 5차시 | 2024.02.14 |  약수, 배수와 소수 |  <a href="https://www.acmicpc.net/problem/17103">다음 소수</a>  | <a href="">2024.02.14</a> |
 | 6차시 | 2024.02.16 |  약수, 배수와 소수 |  <a href="https://www.acmicpc.net/problem/13909">창문 닫기</a>  | <a href="">2024.02.16</a> |
 
+| 8차시 | 2024.02.16 |  스택, 큐, 덱 |  <a href="https://www.acmicpc.net/problem/12789">도키도키 간식드리미</a>  | <a href="">2024.02.16</a> |
+
diff --git "a/wkdghdwns199/\354\212\244\355\205\215_\355\201\220_\353\215\261/ACM-12789.py" "b/wkdghdwns199/\354\212\244\355\205\215_\355\201\220_\353\215\261/ACM-12789.py"
new file mode 100644
index 0000000..497b36f
--- /dev/null
+++ "b/wkdghdwns199/\354\212\244\355\205\215_\355\201\220_\353\215\261/ACM-12789.py"
@@ -0,0 +1,23 @@
+N = int(input())
+order_list = list(map(int, input().split()))
+order = 1
+stack = []
+
+# 5 4 2 3 1
+
+while order_list :
+    if order_list[0] == order:
+        order_list.pop(0)
+        order+=1
+    else :
+        stack.append(order_list.pop(0))
+    
+    while stack :
+        if stack[-1] == order:
+            stack.pop()
+            order +=1
+        else :
+            break
+    
+
+print('Nice') if len(stack)==0 else print('Sad')
\ No newline at end of file