diff --git a/short_version.py b/short_version.py
index 5ba57b9..6741cbf 100644
--- a/short_version.py
+++ b/short_version.py
@@ -4,6 +4,6 @@
 random.seed(1)
 synaptic_weights = 2 * random.random((3, 1)) - 1
 for iteration in xrange(10000):
-    output = 1 / (1 + exp(-(dot(training_set_inputs, synaptic_weights))))
+    output = 1 / (1 + exp(-(dot(training_set_inputs, synaptic_weights))))  # sigmoid function
     synaptic_weights += dot(training_set_inputs.T, (training_set_outputs - output) * output * (1 - output))
 print 1 / (1 + exp(-(dot(array([1, 0, 0]), synaptic_weights))))