diff --git a/README.md b/README.md
index 60c8c9b..ae10169 100644
--- a/README.md
+++ b/README.md
@@ -37,7 +37,7 @@ An example of how you can make explosions in pygame zero.
 
 <u>**How to run:**</u>
 
-To run the example you need PyGame Zero. You can install it by runnig this command:
+To run the example you need PyGame Zero. You can install it by running this command:
 >$ pip3 install pgzero
 
 And to run the example run this command in the main folder:
diff --git a/Tools/macs.py b/Tools/macs.py
new file mode 100644
index 0000000..5bf3523
--- /dev/null
+++ b/Tools/macs.py
@@ -0,0 +1,27 @@
+#!/bin/python3
+
+
+# input string, i.e. "xx:xx:xx:xx:xx:xx,xx:xx:xx:xx:xx:xx"
+macs_raw = "00:04:A5:A3:3B:B0,00:27:22:56:60:8D,00:27:22:56:68:DA,00:27:22:56:69:EC,00:27:22:56:6F:6B,00:27:22:56:6F:6B"
+
+# split the input string of mac address with a ","
+macs = macs_raw.split(",")
+
+def list_duplicates(seq):
+  seen = set()
+  seen_add = seen.add
+  # adds all elements it doesn't know yet to seen and all other to seen_twice
+  seen_twice = set( x for x in seq if x in seen or seen_add(x) )
+  # turn the set into a list (as requested)
+  return list( seen_twice )
+
+# get the duplicates for the list_duplicates() function
+dups = list_duplicates(macs)
+
+# Print number of duplicates
+print("Found %s duplicate(s)." % (len(dups)))
+
+# print a list of all duplicates
+for i in dups:
+    print(i)
+