殚 ㄉㄢ dān 精 ㄐㄧㄥ jīng 竭 ㄐㄧㄝ ˊ jié 虑 ㄌㄩ ˋ lǜ 殫 ㄉㄢ dān 精 ㄐㄧㄥ jīng 竭 ㄐㄧㄝ ˊ jié 慮 ㄌㄩ ˋ lǜ to exhaust one's thoughts and ingenuity (idiom); to think sth through thoroughly to rack one's brains to leave no stone unturned