殫精極慮 dān jīng jí 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

殫 dān utmost, entirely, quite; use up
精 jīng
HSK 4
essence; semen; spirit
極 jí extreme, utmost, furthest, final
慮 lǜ be concerned, worry about