The “first leg” corresponds to {HEAD ~ one leg} of {TAIL ~ the biped walking robot} and the “second leg” corresponds to the other leg thereof 
of
The “ first leg ” corresponds to { HEAD ~ one leg } of { TAIL ~ the biped walking robot } and the “ second leg ” corresponds to the other leg thereof
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH