diff --git a/knapsack/knapsack.py b/knapsack/knapsack.py
index 18a36c3bcdda..941e9c814d16 100644
--- a/knapsack/knapsack.py
+++ b/knapsack/knapsack.py
@@ -20,6 +20,10 @@ def knapsack(capacity: int, weights: list[int], values: list[int], counter: int)
     which is the limit of the capacity.
     """
 
+    # Invalid Case
+    if len(values)!=len(weights):
+    	return -1
+
     # Base Case
     if counter == 0 or capacity == 0:
         return 0