in recent year John successfully settle new job office but John do not like idly sit code compile immediately find interesting distraction the point distraction maintain water level water cooler zebra originally cooler contain exactly k liter water John decide water l liter water r liter John stay office exactly t day he know day exactly x liter water colleague at begin day add exactly y liter water cool point time water cooler range l rNow John wants find able maintain water level necessary level t day help answer question