殚精竭虑 dān jīng jié lǜ

DEFINITIONS

  1. to exhaust one's thoughts and ingenuity (idiom); to think sth through thoroughly
  2. to rack one's brains
  3. to leave no stone unturned

CHARACTERS

殚 dān utmost, entirely, quite; use up
精 jīng
HSK 4
essence; semen; spirit
竭 jié
HSK 6
put forth great effort; exhaust
虑 lǜ
HSK 4
be concerned, worry about