import sys
 
if not sys.argv[1:]:
   mac = raw_input ("Enter MAC address\n")
   print "Mac is %s\n"; % (mac)
   #sys.exit(0)
else:
   mac = sys.argv[1]
   print "Mac is %s\n" % (mac)
 
##I'm checking to see if someone is giving me in the right format
maclen=len(mac)
if maclen == 12:
    ## converting to list, since strings are immuatable
    maclist=list(mac)
    ## defining positions on list
    positions=2,5,8,11,14
 
    for i in positions:
        maclist.insert(i,':')
    ##joining list at the ','
    newmac=",".join(maclist)
    ## stripping ',' out and converting to lowercase.  
    final12mac=newmac.replace(',','').lower()
 
    print final12mac
 
##assuming that 17 characters will either have - or : in MAC address    
elif maclen == 17:
    ##replacing - with : and converting to lowercase
    mac17final=mac.replace('-',':').lower()
    print mac17final
else:
    ## I'm telling them that if it isn't 12 or 17 characters, it has X chars
    print "There are only %s characters" % (maclen)