diff --git a/buggy.py b/buggy.py
--- a/buggy.py
+++ b/buggy.py
@@ -14,7 +14,7 @@
         ans = 0
         for i in range(n):
             if i % 7 == 0 and i != 0:
-                income = a[len(a) - 8]
+                income = a[len(a) - 7]
             ans += income
             income += 1
             a.append(income)
