diff --git a/challenges/grumpyBookstoreOwner/grumpyBookstoreOwner.py b/challenges/grumpyBookstoreOwner/grumpyBookstoreOwner.py
new file mode 100644
index 0000000..9f82e7b
--- /dev/null
+++ b/challenges/grumpyBookstoreOwner/grumpyBookstoreOwner.py
@@ -0,0 +1,10 @@
+def grumpyBookstoreOwner(customers, grumpy, X):
+    nongrumpsum = sum([customers[i] for i in range(len(customers)) if grumpy[i] != 1])
+    customers = [customers[i] if grumpy[i] == 1 else 0 for i in range(len(customers))]
+    sumextra = maxextra = sum(customers[:X])
+    for i in range(X, len(customers)):
+        sumextra += customers[i] - customers[i-X]
+        maxextra = max(maxextra, sumextra)
+    return maxextra + nongrumpsum
+
+assert grumpyBookstoreOwner([1,0,1,2,1,1,7,5], [0,1,0,1,0,1,0,1], 3)