diff --git a/fib.py b/fib.py
index 50722c2..ae8977e 100644
--- a/fib.py
+++ b/fib.py
@@ -6,6 +6,10 @@
 Negative numbers should return None
 """
 def fibonacci(position):
+  if position < 0:
+    print("invalid input")
+  if position == 0: 
+    return 0
   if(position == 1 or position == 2):
     return 1
   return fibonacci(position - 1) + fibonacci(position - 2)