{TAIL ~ The exchange system} invalidates a conventional coupon and prints {HEAD ~ an exchange system coupon} for a product promoted by the coupon exchange system 
{ TAIL ~ The exchange system } invalidates a conventional coupon and prints { HEAD ~ an exchange system coupon } for a product promoted by the coupon exchange system
TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH