Thus, {HEAD ~ the number} of {TAIL ~ times} gas escapes from the valve can be counted 
of
Thus , { HEAD ~ the number } of { TAIL ~ times } gas escapes from the valve can be counted
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH