With the two strings , which are both 16 digits, {TAIL ~ the algorithm} adds {HEAD ~ the two strings}, digit by digit 
With the two strings , which are both 16 digits , { TAIL ~ the algorithm } adds { HEAD ~ the two strings } , digit by digit
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH