diff --git a/boj/28324.py b/boj/28324.py
new file mode 100644
index 0000000..3c22dfa
--- /dev/null
+++ b/boj/28324.py
@@ -0,0 +1,14 @@
+import sys
+input=sys.stdin.readline
+n=int(input().rstrip())
+arr=list(map(int,input().rstrip().split()))
+
+last=0
+result=0
+for i in range(1,n+1):
+    if arr[-i]>last:
+        last+=1
+    elif arr[-i]<last:
+        last=arr[-i]
+    result+=last
+print(result)