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